About Jeff Masters
Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather
By: JeffMasters, 04:58 PM GMT vào 31 Tháng ba, 2010
Record rains from a slow-moving and extremely wet Nor'easter have triggered historic flooding in Rhode Island and Southeastern Massachusetts, with several rivers exceeding their 100-year flood levels. The 16.32" of rain that has fallen on Providence, Rhode Island, this month is the most rain recorded in any month, besting the previous record of 15.38" set in October 2005. Blue Hill Observatory in SE Massachusetts also set a record for wettest month ever, with 18.79" (previous record: 18.78", August 1955.) Records extend back to 1905 and 1885 at the two sites. The Rhode Island all-time state record for heaviest precipitation in a month was smashed as well, thanks to the 19.62" observed this March at North Kingstown. The old state record was 16.70", set at North Foster in October 2005. Many locations in the Northeast recorded their wettest March ever, including New York City and Boston.
Figure 1. Observed precipitation for the month of March. Image credit: NOAA.
From a historical perspective, river flooding in parts of Rhode Island and eastern Massachusetts is expected to rival or exceed the all-time record floods of August 1955, when Hurricanes Connie and Diane hit within one week of each other. Several rivers in the region that set their all-time flood heights just two weeks have set new records this week. It's pretty remarkable that we are having record rainfall and record flooding in the cold season month of March. It's much easier to set records in August, when there is much more moisture in the air available for record rains.
Here is a summary of the major flooding occurring, courtesy of the National Weather Service:
* Pawtuxet River in Rhode Island...flooding will exceed what occurred in middle March. Record-shattering flooding is forecast along the Pawtuxet River through Thursday. Records at the Cranston gauge date back to 1939.
* Blackstone River in Rhode Island...flooding at Woonsocket is forecast to be the worst flooding since the flooding associated with Connie and Diane in 1955. However...due to the heavier rains which have fallen below Woonsocket...flood impacts approaching the 1955 event may be realized.
* Charles River at Dover Massachusetts...near record flooding is forecast. This is expected to be the worst flooding since the flooding associated with Connie and Diane in 1955.
* Neponset River at Norwood Massachusetts...major flooding has already occurred...with a crest of 11.2 feet. This crest is well below the record crest of 14.65 feet which occurred in August 1955 with Connie and Diane.
* Sudbury at Saxonville Massachusetts...record flooding is forecast. This will be the worst flooding since the April 1987 flood.
While the storm responsible for the rains has moved out to sea, there will be a prolonged period of urban and small stream flooding...which should last for at least a couple of days. To keep track of the flood situation, use our wundermap with the USGS river layer turned on.
Severe weather season is here
Two tornadoes occurred near Charlotte, NC on Sunday, March 28, 2010. One of these twisters passed within a few miles of one of the FAA's high-resolution TDWR Doppler radars. Our tornado expert, Dr. Rob Carver, has written an excellent post showing high-resolution images and animations of this tornado.
I'll have a new post on April Fool's Day.
Updated: 06:52 PM GMT vào 31 Tháng ba, 2010
By: JeffMasters, 04:29 PM GMT vào 29 Tháng ba, 2010
Climate change science has come under ferocious attack in recent months. But while it is good to objectively question the science of climate change, much of what is being said in these attacks greatly distorts or makes false statements about what the science says, much to the confusion of the public and policy makers. A resolution passed last month by the South Dakota House is an iconic example of the ignorant falsehoods and distortions common in so many of these recent attacks. By a 36-30 vote, the South Dakota legislature last month passed House Concurrent Resolution 1009, "Calling for balanced teaching of global warming in the public schools of South Dakota." Thirty-four Republicans and two Democrats voted for the resolution, which, remarkably, includes a reference to astrology as being central to the behavior of the weather. Here are the resolutions, put in italics, followed by my comments:
The South Dakota Legislature urges that instruction in the public schools relating to global warming include the following:
(1) That global warming is a scientific theory rather than a proven fact;
This language is identical to what creationists used in their attempts to undermine the teaching of evolution, and is a standard trick used to attack the validity of any established scientific body of evidence. Here's how science works: Scientists collect data about the natural world. Using the aid of such tools as mathematics, scientists then construct theories to explain the observations. These theories must successfully pass review by several experts on the subject before they can be published in a scientific journal. Such "peer reviewed" science is a necessary but not sufficient condition for general acceptance of a theory; alternative theories compete, and the old theory must withstand the test of new theories. The old theory must also be validated by follow-up research by other scientists, who can duplicate the original findings. Gravity is one such theory that is well-supported by the available observations, and has withstood challenges over time. The theory of human-caused climate change is not as mature as the theory of gravity, but it is another theory that is well-supported by the available observations. While a number of alternative theories offering alternative explanations for the recent warming of the planet have been advanced, none of these have come remotely close to gaining widespread acceptance among the scientists publishing peer-reviewed papers on the subject. This is what teachers should be emphasizing to their students, not that "global warming is a scientific theory rather than a proven fact."
(2) That there are a variety of climatological, meteorological, astrological, thermological, cosmological, and ecological dynamics that can effect world weather phenomena and that the significance and interrelativity of these factors is largely speculative;
This is a wildly incorrect statement. "Astrological" refers to the superstitious belief that the movements of the stars and planets can affect the weather. We don't use horoscopes to forecast the weather! "Thermology" is the analysis of detailed infrared images of the human body, and has no relevance to weather. Finally, the laws governing the behavior of the atmosphere are not "largely speculative." Our understanding of these laws has enabled scientists to make computer forecast models that successfully tell us many days in advance what the weather is likely to be. Similar models have been built to study the climate, and these models have been very successful at simulating many aspects of the climate, such as the amount of cooling major volcanic eruptions cause. I would characterize these models as "limited," but they are getting better rapidly, and are not "largely speculative." A few English errors: "interrelativity" isn't a word, and the word "affect" instead of "effect" should have been used in the sentence.
(3) That the debate on global warming has subsumed political and philosophical viewpoints which have complicated and prejudiced the scientific investigation of global warming phenomena;
It's highly ironic that these politicians are complaining about political viewpoints complicating the issue, yet here they are asserting their own political views, laden with awful science, to further complicate things. I agree that the political debate on global warming has complicated its scientific investigation, since climate scientists must now spend time away from their research to defend their work against absurd attacks like this one. Allegations that the debate has "prejudiced" scientific investigation have not been proven, and unproven allegations have no place in an official resolution by lawmakers.
Now, here is the evidence the South Dakota Legislature uses to support their resolutions:
WHEREAS, the earth has been cooling for the last eight years despite small increases in anthropogenic carbon dioxide;
The global temperature trend between 2002 - 2009 was -0.04°C, using the NASA GISS global temperature data set. This trend is not considered mathematically (statistically) significant, meaning that the trend is so close to zero that you can't say the Earth has been cooling. Note that if one picks almost any other period of averaging over the past 40 years, a positive (warming) trend results. For example, the Earth warmed 0.14°C between 2008 and 2009 (though this is also not mathematically significant, since we're only looking at two data points). One needs a lot more data points to get a mathematically significant result, and when one is talking about the climate, it is best to look at 30+ years. The Earth has warmed by about 0.16°C per decade over the past 30 years--a mathematically significant warming trend.
WHEREAS, there is no evidence of atmospheric warming in the troposphere where the majority of warming would be taking place;
Over the 31 years that we have satellite measurements, the lower troposphere has warmed by between 0.13° - 0.15°C per decade. Thus, this statement by the South Dakota legislature is undeniably false. In fact, two of the past four months have seen the warmest temperatures ever measured in the lower atmosphere, according to the University of Alabama, Huntsville. As I've discussed before, the argument made here was in vogue among climate change contrarians prior to 2004, and was the primary method of attack on the validity of global warming theory. However, a series of papers published in 2004 and 2005 showed that global warming theory was correct, and the satellite measurements showing a lack of tropospheric warming were wrong. To continue using a skeptic argument that was discredited five years ago and is no longer used by modern-day contrarians shows a remarkable lack of political savvy on the part of the South Dakota Legislature. They should have taken a lesson from the Utah State Legislature and used the contents of the hacked emails from the University of East Anglia--that is the modern preferred way to attack climate change science. As I've pointed out before, though, these attacks are also bogus.
WHEREAS, historical climatological data shows without question the earth has gone through trends where the climate was much warmer than in our present age. The Climatic Optimum and Little Climatic Optimum are two examples. During the Little Climatic Optimum, Erik the Red settled Greenland where they farmed and raised dairy cattle. Today, ninety percent of Greenland is covered by massive ice sheets, in many places more than two miles thick;
The resolution says "without question" the Earth has gone through warmer climates, then gives one example as the "Little Climatic Optimum," which is the period from around 900 - 1200 A.D. Current climate science, as summarized in the 2007 IPCC report, rates the Little Climatic Optimum as being cooler than the present-day climate, so it is false to say the Little Climatic Optimum was "without question" warmer. Even if it was warmer, that doesn't prove that the modern warming cannot be human-caused (one can use the analogy that different diseases can produce the same symptoms, and a good doctor will perform a scientific examination to determine what is causing the symptoms.) The discussion of the Greenland Ice Sheet makes it sound as if it appeared in the past 1,000 years. That is not the case. The ice coverage of Greenland is similar today to what it was during the time of Erik the Red. Grammar errors: "Earth" should be capitalized. "Erik the Red settled Greenland where they farmed" is grammatically incorrect.
WHEREAS, the polar ice cap is subject to shifting warm water currents and the break-up of ice by high wind events. Many oceanographers believe this to be the major cause of melting polar ice, not atmospheric warming;
While natural wind patterns in the early 1990s are thought to be an important factor that contributed to the decline of the polar ice cap in recent years, I haven't seen any peer-reviewed scientific paper stating that this was the major cause of arctic sea ice loss. Natural wind patterns, warmer atmospheric temperatures, warmer ocean temperatures, and the warming influence of black soot on the ice are all important factors, and there is no consensus on which of these factors is the dominant cause of the melting.
WHEREAS, carbon dioxide is not a pollutant but rather a highly beneficial ingredient for all plant life on earth.
Webster's dictionary defines a pollutant as "man-made waste that contaminates an environment." Webster's defines "contaminate" as "to make inferior or impure." CO2 is man-made waste, and there is scientific evidence that added CO2 can make our atmosphere "inferior" to its present state. As just one example, when CO2 is dissolved in the oceans, the water grows more acidic. Corals and other creatures that build shells out of calcium carbonate cannot form their shells if the acidity passes a critical level--their shells will dissolve. Thus, for these organisms, CO2 is definitely a pollutant. Several shell-building planktonic organisms, such as coccolithophorids, pteropods, and foraminifera, form an important basis of the food chain in cold ocean waters, and the continued increase in CO2 emissions have many scientists very concerned about a collapse of the oceanic food chain in these regions in coming decades. Presumably, the South Dakota lawmakers are taking the very narrow view that a pollutant is something that harms human health when breathed. One other note: they should have said "essential" instead of "highly beneficial" when describing the relationship between CO2 and plant life.
Many scientists refer to carbon dioxide as "the gas of life";
As I discussed at the time, the reference to CO2 being the "gas of life" comes from a fossil-fuel industry-funded ad campaign from 2006, not from the scientific literature.
WHEREAS, more than 31,000 American scientists collectively signed a petition to President Obama stating: "There is no convincing scientific evidence that human release of carbon dioxide, or methane, or other greenhouse gasses is causing or will, in the foreseeable future, cause catastrophic heating of the earth's atmosphere and disruption of the earth's climate.
This a reference to the notorious "Oregon Petition," a product of the Oregon Institute of Science and Medicine (OISM). According to the Institute's web site and the book Climate Cover-up, the Institute is a farm shed situated a couple of miles outside of Cave Junction, OR (population 17,000). The Institute lists seven faculty members, two of whom are dead, and has no ongoing research and no students. It publishes creationist-friendly home-school curricula books on surviving nuclear war. The petition they created in 1999 was sent to scientists and was accompanied by a 12-page "scientific" review of climate change science filled with scientific distortions and falsehoods, printed in exactly the same style used for the prestigious journal, "Proceedings of the National Academy of Sciences." A letter from Dr. Frederick Seitz, who was prominently identified as a former National Academy of Sciences president, accompanied the petition and review (at the time, Seitz was working for the fossil fuel industry-funded George C. Marshall Institute, a pro-industry think tank he helped found.) No doubt, many recipients of the petition took this to be an official National Academy of Sciences communication, and signed the petition as a result. The National Academy of Sciences issued a statement in April 2008, clarifying that it had not issued the petition, and that its position on global warming was the opposite. The petition contains no contact information for the signers, making it impossible to verify. While the petition does carry the names of legitimate scientists who do disagree with the IPCC consensus on the reality and dangers of human-caused climate change, the fraudulent way the petition was presented and the impossibility of verifying the signatures make its relevance highly questionable. An excellent post at skepticalscience.com explores the Oregon Petition's claim of 31,000 signatures in greater detail. It turns out that anyone can sign the petition and claim they are a scientist; there is no verification. The requirements for being a scientist include anyone with a Bachelor's degree in any of the following fields:
* Atmosphere, Earth, and Environment fields: atmospheric science, climatology, meteorology, astronomy, astrophysics, earth science, geochemistry, geology, geophysics, geoscience, hydrology, environmental engineering, environmental science, forestry, oceanography
* Computers and Math: computer science, mathematics, statistics
* Physics and Aerospace: physics, nuclear engineering, mechanical engineering, aerospace engineering
* Chemistry: chemistry, chemical engineering
* Biochemistry, Biology, and Agriculture: biochemistry, biophysics, biology, ecology, entomology, zoology, animal science, agricultural science, agricultural engineering, plant science, food science
* Medicine: medical science, medicine
* General Engineering and General Science: engineering, electrical engineering, metallurgy, general science
The skepticalscience.com post argues, "if we remove all the engineers, medical professionals, computer scientists, and mathematicians, then the 31,478 "scientists" turn into 13,245 actual scientists, as opposed to scientists according to the OISM's expansive definition." This represents 0.1% of the estimated 10.6 million scientists in the U.S. Now, let's consider specialists in climate change. The American Geophysical Union (AGU) has over 55,000 members, of which over 7,200 claim that atmospheric sciences is their primary field. The OISM claims 152 atmospheric scientists. Compared to the atmospheric scientist membership in the AGU, the OISM signatories are only 2.1%, and this estimate is high given the fact that the AGU does not claim all atmospheric scientists as members.
Counterbalancing the fraudulently obtained and inflated "consensus" of the Oregon Petition are the official climate change position statements of the following scientific organizations, which all agree with the consensus that "most of the global warming in recent decades can be attributed to human activities:"
American Association for the Advancement of Science
American Astronomical Society
American Chemical Society
American Geophysical Union
American Institute of Physics
American Meteorological Society
American Physical Society
Australian Coral Reef Society
Australian Meteorological and Oceanographic Society
British Antarctic Survey
Canadian Foundation for Climate and Atmospheric Sciences
Canadian Meteorological and Oceanographic Society
U.S. Environmental Protection Agency
European Federation of Geologists
European Geosciences Union
European Physical Society
Federation of American Scientists
Federation of Australian Scientific and Technological Societies
Geological Society of America
Geological Society of Australia
International Union for Quaternary Research (INQUA)
International Union of Geodesy and Geophysics
National Center for Atmospheric Research
National Oceanic and Atmospheric Administration
Royal Meteorological Society
Royal Society of the UK
The Academies of Science from 19 different countries all endorse the consensus. Eleven countries have signed a joint statement endorsing the consensus position:
Academia Brasiliera de Ciencias (Brazil)
Royal Society of Canada
Chinese Academy of Sciences
Academie des Sciences (France)
Deutsche Akademie der Naturforscher Leopoldina (Germany)
Indian National Science Academy
Accademia dei Lincei (Italy)
Science Council of Japan
Russian Academy of Sciences
Royal Society (United Kingdom)
National Academy of Sciences (USA) (12 Mar 2009 news release)
A letter from 18 major scientific organisations to the U.S. Congress in October 2009 states:
"Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that the greenhouse gases emitted by human activities are the primary driver. These conclusions are based on multiple independent lines of evidence, and contrary assertions are inconsistent with an objective assessment of the vast body of peer-reviewed science."
The consensus is also endorsed by a Joint statement by the Network of African Science Academies (NASAC), the Royal Society of New Zealand, and the Polish Academy of Sciences.
One can read much more on the topic at the excellent skepticalscience.com blog where I took this information from.
Moreover, there is substantial scientific evidence that increases in atmospheric carbon dioxide will produce many beneficial effects on the natural plant and animal environments of the earth."
This is true, but of course neglects to mention the many harmful effects warmer temperatures will bring.
On to the Senate
The South Dakota Senate passed by a vote of 18-17 an amended version of the resolution which eliminated most of the scientific falsehoods and distortions and corrected most of the English errors (except for the use of the non-word "interrelativity.") However, the resolution still asserts that the global warming debate has prejudiced the scientific investigation of global climatic change phenomena. The amended version now returns to the House for approval.
The fundamental scientific ignorance displayed by the South Dakota legislature clearly makes them unqualified to recommend how science should be taught in schools. While the proposed resolution by the South Dakota legislature does not have the force of law, the debate on climate change is too important to be based on falsehoods and distortions made up by politicians or by the "Manufactured Doubt Industry." Politicians should stay out of micro-managing education, and leave the teaching to the teachers.
For further reading
Our Climate Change blogger, Dr. Ricky Rood, has an excellent post discussing politics and global warming, titled, If Lady Chatterley's Lover, then...
The New York Times has an interesting article, Darwin Foes Add Warming to Targets, that discusses how several states have introduced or approved measures mandating that opposing views on human-caused climate change and evolution should be taught in the classroom.
Updated: 05:54 PM GMT vào 29 Tháng ba, 2010
By: JeffMasters, 09:05 PM GMT vào 24 Tháng ba, 2010
It's been a busy past two months of weather and climate change news, and I haven't found time to blog about the research presented at December's American Geophysical (AGU) meeting in San Francisco. That is the world's largest scientific conference on climate change, and the place to be if you want to get the pulse of the planet. The keynote speech at the AGU meeting was given by Dr. Richard Alley of Penn State University. Dr. Alley is the Evan Pugh Professor of Geosciences at the Pennsylvania State University, and one of the most respected and widely published world experts on climate change. Dr. Alley has testified before Congress on climate change issues, served as lead author of "Chapter 4: Observations: Changes in Snow, Ice and Frozen Ground" for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), and is author of more than 170 peer-reviewed scientific articles on Earth's climate. He is also the author of a book I highly recommend--The Two Mile Time Machine, a superb account of Earth's climate history as deduced from the 2-mile long Greenland ice cores. A standing-room only audience of over 2,000 scientists packed the lecture hall Dr. Alley spoke at, and it was easy to see why--Alley is an excellent and engaging speaker. I highly recommend listening to his 45-minute talk via a very watchable recording showing his slides as he speaks in one corner of the video. If you want to understand why scientists are so certain of the link between CO2 and Earth's climate, this is a must-see lecture.
Figure 1. Dr. Richard Alley of Penn State University, delivering the keynote speech at the 2009 AGU conference on climate change.
The Biggest Control Knob: CO2 in Earth's Climate History
Earth's past climate has been shaped by a number of key "control knobs"--solar energy, greenhouse gas levels, and dust from volcanic eruptions, to name the three main ones. The main thrust of Dr. Alley's speech is that we have solid evidence now--some of it very new--that CO2 has dominated Earth's climate over the past 400 million years, making it the climate's "biggest control knob". Dr. Alley opens his talk by humorously discussing a letter from an irate Penn State alumnus. The alumnus complains that data of temperatures and CO2 levels from ice cores in Antarctica don't match:
"CO2 lags Earth's temperature...This one scientific fact which proves that CO2 is not the cause of recent warming, yet...Dr. Alley continues to mislead the scientific community and the general public about 'global warming'. His crimes against the scientific community, PSU, the citizens of this great country, and the citizens of the world are significant and must be dealt with severely to stop such shameful activities in the future".
Dr. Alley explains that the irate alumnus is talking about the Antarctic ice core record, which shows that as we emerged from each ice age, the temperature began increasing before the CO2 did, so increased CO2 was not responsible for the warmings that brought us out of these ice ages. Climate change scientists and skeptics alike agree that Earth's ice ages are caused by periodic variations in Earth's orbit called Milankovich Cycles. "There's no doubt that the ice ages are paced by the orbits", says Dr. Alley. "No way that the orbit knows to dial up CO2, and say 'change'. So it shouldn't be terribly surprising if the CO2 lags the temperature change. The temperature never goes very far without the CO2. The CO2 adds to the warming. How do we know that the CO2 adds to the warming? It's physics!"
Dr. Alley then discusses that the physics that govern how CO2 absorbs and re-emits heat energy, when plugged into state-of-the-art climate models, show that about half of the observed 5 - 6°C natural warming that occurred since the last ice age ended was due to extra CO2 added to the atmosphere. At the peak of the Ice Age, CO2 was about 190 ppm. By the end, it was about 280 ppm (Figure 1). Earth's orbital variations "forced" a warming, which caused more CO2 to escape from swamps and oceans, with a time lag of several centuries. The increased CO2 reinforced the warming, to double what it would have been otherwise--a positive feedback loop. "Higher CO2 may be forcing or feedback--a CO2 molecule is radiatively active regardless of how it got there", says Dr. Alley. "A CO2 molecule does not remember why it is there--it only remembers that it is there". In other words, the fact that higher CO2 levels did not trigger an end to the Ice Age does not mean that the CO2 had no warming effect. Half of the the observed 5 - 6°C natural warming that occurred since the last ice age ended was due to the extra CO2 added to the atmosphere. So, the irate PSU alumnus was half right. The CO2 does lag temperature. However, we can only explain approximately half of the warming since the last ice age ended if we leave out the increase in CO2 that has occurred. "If higher CO2 warms, Earth's climate history makes sense, with CO2 having caused or amplified the main changes. If CO2 doesn't warm, we have to explain why the physicists are so stupid, and we also have no way to explain how a lot of really inexplicable climate events happened over Earth's history. It's really that simple. We don't have any plausible alternative to that at this point".
Figure 2. Ice core record from Vostok, Antarctica, showing the near-simultaneous rise and fall of Antarctic temperature and CO2 levels through the last 350,00 years, spanning three ice age cycles. However, there is a lag of several centuries between the time the temperature increases and when the CO2 starts to increase. Image credit: Marian Koshland Science Museum of the National Academy of Sciences: Global Warming Facts and Our Futures, originally provided to that site by Kurt Cuffey, University of California, Berkely.
CO2 and temperatures rise and fall in synch
Dr. Alley continues with a discussion of how CO2 and temperature levels have risen and fallen in synch over most of geologic time. But for many years there was still a mystery: occasionally there were eras when temperature changes did not match CO2 changes. But new paleoclimate research, much of it just in the past two years, has shown that nearly all of these mis-matches were probably due to suspect data. For example, the mismatch in the Miocene Era has significantly improved, thanks to a new study published this year by Tripati et al. Another example occurs during the Ordovician Era 444 million years ago, as discussed in a recent post at the excellent skepticalscience.com blog.
Figure 3. Atmospheric CO2 and continental glaciation, 400 million years ago to the present. The vertical blue bars mark where ice ages have occurred. The length of the blue bars corresponds to how close to the Equator the ice sheets got (palaeolatitude, scale on the right side of the plot). The left scale shows atmospheric CO2 over the past 400 million years, as inferred from a model (green area) and from four different "proxy" fossil sources of CO2 information. This is Figure 6.1 of the Palaeoclimate chapter of the 2007 IPCC report.
Is there anything else we should be worried about?
Dr. Alley continues with a discussion of other influences that may be able to explain global warming, such as volcanos, changes in solar output, and cosmic rays. A whole bunch of the competing hypotheses don't work", says Dr. Alley. "When there's a bunch of big volcanos, they make it cool. If volcanos could get organized, they'd rule the world. There might be a tiny bit of organization due to flexing of the crust, but they're not controlling the world".
Regarding solar changes: "When the sun changes, it does seem to show up in the temperature record. As far back as we can see well, the sun is friendly, it doesn't change much. If the sun changed a lot, it would control things hugely. But it only changes really slowly--as far as we can tell. The record doesn't go back as far as we'd like, and there's work to be done here--but it just doesn't seem to be doing much".
Figure 4. Greenland ice core proxy measurements of temperature (top curve) and cosmic ray flux (bottom curve) for the past 60,000 years. The Earth's magnetic field weakened by 90% 40,000 years ago, for a period of about 1,000 years, but there was no change seen in the temperatures in Greenland.
Regarding cosmic rays: "The sun doesn't change much, but the sun modulates the cosmic rays, the cosmic rays modulate the clouds, the clouds modulate the temperature, and so the sun is amplified hugely. It's really interesting hypothesis, there's really good science to be done on this, but there's reason to think its a fine-tuning knob". He goes on to show an ice core example from a period 40,000 years ago (Figure 4) where the Earth magnetic field had near-zero strength for hundreds of years. This allowed a massive flux of cosmic rays to penetrate to the Earth's surface, creating a huge spike in ice core Beryllium-10, a radionuclide made by cosmic rays. If cosmic rays were important to climate, we would expect to see a corresponding major swing in temperature, but the ice core shows no change during the period of enhanced cosmic ray bombardment 40,000 years ago. "We had a big cosmic ray signal, and the climate ignores it", Dr. Alley comments.
How sensitive is climate to a doubling of CO2?
The IPCC report talks extensively about computer climate models' calculations of "climate sensitivity"--how much Earth's climate would warm if CO2 doubled from pre-industrial levels of 280 ppm, to 560 ppm (we're currently at 390 ppm). A mid-range number from the 2007 IPCC report often used by climatologists is that the climate sensitivity is 3°C for a doubling of CO2. Dr. Alley takes a look at what paleoclimate has to say about the climate sensitivity to CO2. "The models actually do pretty well when you compare them to the past. The best fit is 2.8°C.
Dr. Alley concludes, "Where we really stand now, is, we're not quite at the pound on the table, this story is very clearly not done. But an increasing body of science indicates that CO2 has been the most important controller of global average climate of the Earth."
I'll have a new post Sunday or Monday.
Updated: 08:40 PM GMT vào 21 Tháng tư, 2013
By: JeffMasters, 08:36 PM GMT vào 22 Tháng ba, 2010
Massive duststorms swept through China over the weekend, bringing record air pollution and near-zero visibility to large regions of eastern China, Hong Kong, and Taiwan. The dust will reach South Korea on Tuesday. The dust was kicked up by the strong winds of a cold front that crossed China on Saturday. The winds passed over regions of Mongolia and northwest China that have been suffering from an extended drought. Overgrazing, deforestation, and urban sprawl have combined with the drought to create large regions of new desert with loose soil that was the source of dust for this weekend's duststorm. Heavy duststorms have brought increasing amounts of dangerous particulate matter to Beijing and much of eastern China in recent years, due to the worsening desertification. Beijing issued its highest level of air pollution alert, Level 5, on Saturday.During the height of the duststorm, winds were sustained at 34 mph, gusting to 45 mph, with visibility 1 - 2 miles in heavy dust. Conditions have improved slightly to Level 4 pollution today.
Figure 1. This natural-color image from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite shows the dust storm on Saturday, March 20, 2010. Few landmarks or topographic features are recognizable beneath the dust, which covers the lower half of the image and wraps around the right-hand side in a comma shape that terminates in a large ball of dust near image center. The head of the comma marks a center of low pressure of a mid-latitude cyclone crossing the country. Image credit: NASA.
Figure 2. Drought conditions based on a 2-year deficit of precipitation, using the Standard Precipitation Index (SPI). Image credit: UK Global Drought Monitor.
Record air pollution in Hong Kong
The dust storms have brought extremely hazardous air quality to Hong Kong, which has recorded is worst air pollution levels since monitoring began in 1995. Pollution levels Monday were 12 to 14 times the amount recommended by the World Health Organization, and topped out at 400 points. An index of 100 points is considered "very high", 200 is "severe", and can lead to coughing, phlegm and sore throats. The previous record highest pollution level was 202, set in July 2008.
I'll have a new post Wednesday or Thursday.
By: JeffMasters, 03:08 PM GMT vào 19 Tháng ba, 2010
The Red River at Fargo, North Dakota continues to rise, with a peak expected Sunday at the 4th highest flood level observed in the past century. "Major" flood level is 30 feet, which the river surpassed on Wednesday, and the river is expected to crest near 38 feet on Sunday, just 2.8 feet below the record set last year. Flood stage is eighteen feet, and the Red River has now reached flood stage at Fargo for eighteen consecutive years, according to the U.S. Army Corps of Engineers. Prior to this remarkable stretch of flooding (which began in 1993), the river flooded in just 29 of 90 years. This year's flood is rated as somewhere between a 50-year and 100-year flood. Last year's record flood was a 100-year flood. The U.S. Army Corps of Engineers lists the 10-year flood level for the Red River at Fargo to be 10,300 cubic feet per second. A 10-year flood, historically, has a 10% chance of occurring in a given year. In the last twenty years, the Red River has had eight 10-year floods--one every 2.5 years, on average. This year is the fourth year out of the past five with a 10-year flood. Clearly, flooding has increased significantly along the Red River over the past twenty years.
Figure 1. Current and forecast flood stage for the Red River of the North at Fargo, ND. You can access images like these using our wundermap for Fargo with the "USGS River" layer turned on. Click on the icon for USGS station 05054000, then hit the "click for graph" link.
Reasons for flooding: landform factors
According the U.S. Geological Survey, the unique landform characteristics of the Red River Valley make it highly susceptible to flooding. These factors include:
1) A relatively shallow and meandering river channel--a shallow channel holds less water and the meandering can cause flow to slow down as the channel makes its turns, causing over-bank flooding.
2) A gentle slope (averaging 0.5 to 1.5 feet per mile) that inhibits channel flow and encourages overland flooding or water "ponding" (especially on even, saturated ground) in the basin.
3) The northerly direction of flow--flow in the Red River travels from south (upstream) to north (downstream). The direction of flow becomes a critical factor in the spring when the southern (upstream) part of the Red River has thawed and the northern (downstream) part of the channel is still frozen. As water moves north toward the still frozen river channel, ice jams and substantial backwater flow and flooding can occur.
Figure 2. Peak flow of the Red River at Fargo, North Dakota through time. The two largest flow rates occurred last year (2009), and in 1997. The projected crest for Sunday (red circle) would be fourth greatest flood since reliable records began in 1901. Image credit: U.S. Geological Survey.
Reasons for this year's flood: highly unfavorable weather conditions
The USGS also cites five weather factors that can act to enhance flooding along the Red River. All five of these factors occurred to a significant degree this year:
1) Above-normal amounts of precipitation in the fall of the year that produce high levels of soil moisture, particularly in flat surface areas, in the basin. North Dakota had its 22nd wettest fall in the 115-year record in 2009.
2) Freezing of saturated ground in late fall or early winter, before significant snowfall occurs, that produces a hard, deep frost that limits infiltration of runoff during snowmelt. Fargo had a November that was much warmer than average, followed by a sudden plunge to below-zero temperatures by the second week of December. This froze the saturated ground to a great depth.
3) Above-normal winter snowfall in the basin. North Dakota had a top 15% winter for precipitation, with the period December 2009 - February 2010 ranking 15th wettest in the past 115 years.
4) Above-normal precipitation during snowmelt. Precipitation for March 1 - 18 has been 1.41", compared to the average of 0.61".
5) Above-normal temperatures during snowmelt. High temperatures in Fargo have averaged 6°F warmer than normal for March 1 - 18.
Urbanization increases flooding
Urbanization has had a major impact on increasing flooding not only along the Red River, but in every river basin in the U.S. Many cities and developed areas are located in flood plains next to major rivers and their tributaries. Highways, streets, parking lots, sidewalks, and buildings now cover large areas of the ground that used to absorb excess rain water and slow the rate at which run-off from precipitation and melting snow reached rivers. By developing large portions of our flood plains, run-off now reaches rivers more quickly, generating higher floods.
Building levees and flood defenses increases flood peaks
Defending ourselves against floods has made floods worse. Every time a new levee is built, or an old floodwall raised in height to prevent overtopping, more and more water is forced into the river bed, which raises the height of the flood. Flood waters that used to be able to spread out over their natural flood plains are now forbidden from spilling out over newly developed land in flood plains. For example, proposed improvements to the flood defense system in Fargo could cause a 4 - 10 inch rise in floods immediately downstream from the city, according to the Army Corps of Engineers.
Precipitation is increasing
As the climate warms, evaporation of moisture from the oceans increases, resulting in more water vapor in the air. According to the 2007 IPCC report, water vapor in the global atmosphere has increased by about 5% over the 20th century, and 4% since 1970. Satellite measurements (Trenberth et al., 2005) have shown a 1.3% per decade increase in water vapor over the global oceans since 1988. Santer et al. (2007) used a climate model to study the relative contribution of natural and human-caused effects on increasing water vapor, and concluded that this increase was "primarily due to human-caused increases in greenhouse gases". This was also the conclusion of Willet et al. (2007). This increase in water vapor has very likely led to an increase in global precipitation. For instance, over the U.S., where we have very good precipitation records, annual average precipitation has increased 7% over the past century (Groisman et al., 2004). Precipitation over the Red River drainage basin increased by about 10 - 20% during the 20th Century (Figure 3.) The same study also found a 14% increase in heavy (top 5%) and 20% increase in very heavy (top 1%) precipitation events over the U.S. in the past century. These are the type of events most likely to cause flooding. Kunkel et al. (2003) also found an increase in heavy precipitation events over the U.S. in recent decades, but noted that heavy precipitation events were nearly as frequent at the end of the 19th century and beginning of the 20th century, though the data is not as reliable back then.
Figure 3. Change in precipitation over the U.S. between 1900 - 2000, from the U.S. Cooperative network. Precipitation in the Red River drainage area increased by 10 - 20% over the 20th century. Image credit: Contemporary Changes of the Hydrological Cycle over the Contiguous United States: Trends (Groisman et al., 2002).
The future of flooding
As the population continues to expand, development in flood plains and construction of new levees and flood protection systems will continue to push floods to higher heights. With global warming expected to continue and drive ever higher precipitation amounts--falling preferentially in heavy precipitation events--it is highly probable that flooding in the Red River Valley--and over most of the northern 2/3 of the U.S. where precipitation increases are likely--will see higher and more frequent floods. With these higher and more frequent floods comes the increased risk of multi-billion dollar disasters, when a record flood event overwhelms flood defenses and inundates huge areas of developed flood plains. Obviously, we need to make smart decisions to limit development in flood plains to reduce the cost and suffering of these future flooding disasters.
Kunkel, K. E., D. R. Easterling, K. Redmond, and K. Hubbard, 2003, "Temporal variations of extreme precipitation events in the United States: 1895.2000", Geophys. Res. Lett., 30(17), 1900, doi:10.1029/2003GL018052.
Groisman, P.Y., R.W. Knight, T.R. Karl, D.R. Easterling, B. Sun, and J.H. Lawrimore, 2004, "Contemporary Changes of the Hydrological Cycle over the Contiguous United States: Trends Derived from In Situ Observations," J. Hydrometeor., 5, 64.85.
Milly, P.C.D., R.T. Wetherald, K.A. Dunne, and T.L.Delworth, Increasing risk of great floods in a changing climate", Nature 415, 514-517 (31 January 2002) | doi:10.1038/415514a.
Santer, B.D., C. Mears, F. J. Wentz, K. E. Taylor, P. J. Gleckler, T. M. L. Wigley, T. P. Barnett, J. S. Boyle, W. Brüggemann, N. P. Gillett, S. A. Klein, G. A. Meehl, T. Nozawa, D. W. Pierce, P. A. Stott, W. M. Washington, and M. F. Wehner, 2007, "Identification of human-induced changes in atmospheric moisture content", PNAS 2007 104: 15248-15253.
Trenberth, K.E., J. Fasullo, and L. Smith, 2005: "Trends and variability in column-integrated atmospheric water vapor", Climate Dynamics 24, 741-758.
Willett, K.M., N.P. Gillett, P.D. Jones, and P.W. Thorne, 2007, "Attribution of observed surface humidity changes to human influence", Nature 449, 710-712 (11 October 2007) | doi:10.1038/nature06207.
A good way to track the flooding event is to use our wundermap for the Red River with the USGS River layer turned on.
The Fargo Flood webpage of North Dakota State University, Fargo, has some excellent links.
I'll have a new post on Monday or Tuesday.
Updated: 07:34 PM GMT vào 19 Tháng ba, 2010
By: JeffMasters, 12:51 PM GMT vào 18 Tháng ba, 2010
The globe recorded its sixth warmest February since record keeping began in 1880, according to the National Oceanic and Atmospheric Administration's (NOAA's) National Climatic Data Center. NASA's Goddard Institute for Space Studies rated February 2010 the second warmest, behind 1998. The year-to-date period, January - February, is the 5th or 2nd warmest such period on record, according to NOAA and NASA, respectively. NOAA rated February 2010 global ocean temperatures as the 2nd warmest on record, next to 1998. February land temperatures in the Southern Hemisphere were the warmest on record, but in the Northern Hemisphere, they were the 26th warmest. The relatively cool Northern Hemisphere land temperatures were due in part to the much-above average amount of snow on the ground--February 2010 snow cover in the Northern Hemisphere was the 3rd highest in the 44-year snow cover record. For the entire winter, the Northern Hemisphere had the 2nd greatest snow cover on record, the U.S. had its greatest snow cover, and Eurasia had its 4th most.
Figure 1. departure of surface temperature from average for the globe during February 2010. Image credit: National Climatic Data Center.
Global satellite-measured temperatures for the lowest 8 km of the atmosphere were the second warmest on record in February, according to both the University of Alabama Huntsville (UAH) and Remote Sensing Systems (RSS) groups. Both groups also rated the winter of 2009 - 2010 the 2nd warmest winter on record. The record warmest February and winter occurred 1998.
Moderate El Niño conditions continue
Moderate El Niño conditions continue over the tropical Eastern Pacific. Ocean temperatures in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region", were at 1.2°C above average--in the middle of the 1.0°C - 1.5°C range for a moderate El Niño--on March 14, 2010, according to the Australian Bureau of Meteorology. The strength of El Niño has been roughly constant for all of February and the first two weeks of March. Anomalously strong westerly winds along the Equator that have helped maintain the current El Niño have weakened since March 1, but are probably strong enough to maintain the current moderate El Niño conditions through mid-April. Some slow weakening of El Niño is likely beginning in early April. It is highly uncertain what may happen to El Niño at that point, with the models split between predicting a weak El Niño, neutral conditions, or a La Niña by the height of hurricane season (August-September-October). It's worth noting that the last time we had a strong El Niño--the record-strength 1997 - 1998 event--El Niño conditions collapsed suddenly in May 1998, and a La Niña event rapidly developed during the summer of 1998. A similar chain of events is possible this year, as well. However, the El Niño of 1986 - 1987 maintained moderate strength through two consecutive hurricane seasons, and it is possible that this year's El Niño could pull a similar feat. We simply don't have the predictive skill to say what might happen to El Niño this summer.
February sea ice extent in the Arctic 4th lowest on record
February 2010 Northern Hemisphere sea ice extent was the 4th lowest since satellite measurements began in 1979. Ice extent was lower than in 2009 and 2008, but greater than in 2005, 2006, and 2007, according to the National Snow and Ice Data Center (NSIDC). The weather pattern over the Arctic during much of February 2010 featured a strongly negative Arctic Oscillation (AO). This pattern tends to slow the winds that typically flush large amounts of sea ice out of the Arctic between Greenland and Iceland. In this way, a negative AO could help retain some the second- and third-year ice through the winter, and potentially rebuild some of the older, multi-year ice that has been lost over the past few years.
Heavy damage on Fiji from Tropical Cyclone Tomas
Communications are still out to most of the islands in the Fiji devastated by Tropical Cyclone Tomas, but it is apparent that the Category 3 storm caused "overwhelming damage" to the islands that received a direct hit, according to the Associated Press. Tomas, packing winds of up to 130 mph (205 kph) at its center, hit Fiji beginning late Friday. The Lau and Lomaiviti island groups and the northern coast of the second biggest island, Vanua Levu, took the brunt of the storm. Only one death has been reported thus far. Initial reports said 1500 homes were destroyed or damaged and up to 50 percent of facilities in the Lau Group were affected.
I'll have a new post on Friday, when I plan to discuss why the Red River at Fargo, ND is now experiencing a "10-year flood" once every 2.5 years, on average.
Updated: 12:52 PM GMT vào 18 Tháng ba, 2010
By: JeffMasters, 02:51 PM GMT vào 16 Tháng ba, 2010
The extremely wet and windy Nor'easter that plowed across the northern tier of states has left moderate to major flooding in its wake over both the Midwest and Northeast. In the Northeast, the storm dropped more than five inches of rain in New Jersey, Massachusetts, Rhode Island, and Connecticut, and moderate to major flooding is occurring in these states. Flooding was particularly severe in Rhode Island on the Pawtuxet River in Cranston, where the river crested a record six feet over flood stage, forcing evacuations. Major flooding was also occurring in New Jersey, where the Passaic River at Little Falls is cresting at five feet over flood stage.
In the Midwest, snow melt and heavy rains have swollen the Red River in North Dakota and Minnesota to near flood stage, and the river is expected to crest two feet above major flood stage by Sunday morning, and one foot above one of the permanent dikes on the river. In Fargo, ND, the Red River is expected to crest Saturday at 38 feet, three feet below the record of 41 feet set last year. Many rivers in Iowa are in flood and expected to crest above major flood stage on Thursday or Friday this week, including the Des Moines River in northern Iowa. In Des Moines, flooding on the Des Moines River is expected to be moderate, but a levee that failed in the floods of 1993 and 2008 is leaking, and residents of the area are evacuating, according to media reports.
Figure 1. Estimated precipitation for the seven day period ending at 8am EDT Monday March 15, 2010. Image credit: NOAA.
Tropical Cyclone Tomas roars through Fiji Islands
Tropical Cyclone Tomas roared through the eastern portion of the Fiji Islands as a major Category 3 storm with 130 mph winds yesterday. Tomas sideswiped the two largest islands in the chain, destroying 50 buildings, causing extensive power outages, and claiming one life. The cyclone made a direct hit on several of the smaller islands to the east of the main islands, and the extent of damage on these islands is unknown, but undoubtedly very heavy.
Tropical Cyclone Ului weakens, may threaten Australia
The first Category 5 tropical cyclone of the year, Tropical Cyclone Uliu, has weakened from its impressive peak as a Category 5 storm with 160 mph winds to a low-end Category 4 storm with 132 mph winds. Ului is over the open waters of the South Pacific, east of Australia, and is projected to significantly decay as the week progresses, due to high wind shear. Ului may be a threat to the Queensland coast of Australia by the end of the week, but should be at tropical storm strength by then.
Figure 2. Tropical Cyclone Ului (left) and Tropical Cyclone Tomas (right). Over the Solomon Islands, Tropical Cyclone Ului had maximum sustained winds of 130 knots (240 kilometers per hour, 150 miles per hour) and gusts up to 160 knots (300 km/hr, 180 mph). Over Fiji, Tropical Cyclone Tomas had maximum sustained winds of 115 knots (215 km/hr, 132 mph) and gusts up to 140 knots (260 km/hr, 160 mph). The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra and Aqua satellites captured both storms in multiple passes over the South Pacific on March 15, 2010, local time. The majority of the image is from the morning of March 15 (late March 14, UTC time) as seen by MODIS on the Terra satellite, with the right portion of the image having been acquired earliest. The wedge-shaped area right of center is from Aqua MODIS, and it was taken in the early afternoon of March 15 (local time). Image credit: NASA.
Portlight looks to build permanent shelters in Haiti
On February 26th, torrential rains brought more than five feet (1.5 m) of flood water into the streets in the coastal city of Les Cayes, Haiti, an area unscathed by the massive January 2010 earthquake. Eleven people were killed during this storm, with the rainy season still two months away. This deadly flood serves as a reminder that the people of Haiti are highly vulnerable to disastrous flooding during this year's rainy season. A vast number of the survivors are living in "tent" cities where most of the "tents" are really nothing more than bed sheets draped over ropes and sticks; the potential for a second humanitarian disaster is significant. With this in mind, Portlight.org has been exploring fast, inexpensive methods of providing solid, permanent, safe shelter for survivors of the earthquake. They have found a number of groups looking at using shipping containers for this purpose. Shipping containers are steel-reinforced boxes used for shipping goods overseas. Portlight's on-site coordinator in Haiti, Richard Lumarque, has identified an engineer that has come up with a number of designs for converting these containers into dormitories, offices, medical facilities and individual homes; his plan for a dormitory container is below. Portlight is looking to help with this effort; please visit the Portlight.org web site to learn more and to donate to this worthy cause.
Figure 3. A proposed design for a simple dormitory that can accommodate twelve people, built from a shipping container.
I'll have a new post on Wednesday or Thursday.
Updated: 02:55 PM GMT vào 16 Tháng ba, 2010
By: JeffMasters, 01:25 PM GMT vào 15 Tháng ba, 2010
An extremely wet and windy Nor'easter whipped through the Mid-Atlantic and Northeastern U.S. over the weekend, dropping rains in excess of six inches over some regions, and driving high winds gusting near hurricane force. On Saturday afternoon, JFK Airport in New York City recorded sustained winds of 45 mph, gusting to hurricane force--75 mph. Soils already saturated from run-off due to all the melting snow from the heavy winter snows have been unable to absorb the heavy rains. As a result, there is widespread minor to moderate river flooding, and many power poles have toppled due to the high winds and wet soil. Over half a million people were without power in the region over the weekend. The Nor'easter will continue to bring strong winds and moderate rain to the region today, then gradually weaken and move away from the Northeast on Tuesday.
Figure 1. Estimated precipitation from the weekend Nor'easter over the Northeast. Rainfall amounts in excess of six inches (pink colors) occurred in New York and Connecticut.
Ului: first Category 5 storm of the year
The first Category 5 tropical cyclone of the year has arrived. Over the weekend, Tropical Cyclone Uliu intensified into a lower-end Category 5 storm with 160 mph winds in the open waters of the South Pacific, east of Australia. Ului has weakened slightly into a still-powerful Category 4 storm with 150 mph, but is projected to significantly decay as the week progresses, due to high wind shear. Some of the models foresee that Ului will be a long-range threat to the Queensland coast of Australia by the end of the week, but the storm should be in a much weakened state by then, and may also turn out to sea without hitting land. Australia has had a remarkably easy hurricane season so far--no tropical cyclones entered Australian waters during the month of February, the first time that has happened since 1944. That would be equivalent to the U.S. having no tropical storms near our coast in the hurricane-prone month of August.
Figure 1. Tropical Cyclone Ului at peak strength at 22:22 UTC Saturday, March 13. At the time, Ului was a Category 5 storm with 160 mph winds and a minimum pressure of 918 mb. Image credit: NRL Monterey.
Tropical Cyclone Tomas
Meanwhile, Category 3 Tropical Cyclone Tomas is causing trouble in the Fiji Islands, where the cyclone's 125-mph sustained winds are being felt in the less populated eastern islands. Tomas has already claimed one life, ripped off roofs, and caused extensive power outages in the Fiji Islands, according to news reports. However, the cyclone is missing the two largest and most populated islands.
I'll have a new post on Tuesday.
By: JeffMasters, 03:26 PM GMT vào 12 Tháng ba, 2010
The U.S. just experienced its coldest winter in 25 years, according to the National Climatic Data Center. The winter period December - February was the 18th coldest winter in the contiguous U.S. over the past 115 years, and the coldest since 1984 - 1985. It was also a wet winter, ranking 19th wettest. The states experiencing the coldest winters, relative to average, were Texas and Louisiana, which had their 5th coldest winters on record. Mississippi, Georgia, Alabama, Oklahoma, Arkansas, Florida, and South Carolina also had a top-ten coldest winter. The only state much above average was Maine, which had its 3rd warmest winter. As I discussed earlier this week, this winter's cold weather over the U.S. is largely due to the Arctic Oscillation/North Atlantic Oscillation, which assumed its most extreme negative configuration since record keeping began in 1950. El Niño helped keep things cool from Texas to the Southeastern U.S., as well.
Figure 1. Winter temperatures for the winter of 2009 - 2010. Image credit: National Climatic Data Center.
A cold February in the U.S.
February temperatures were 2.2°F below average across the contiguous U.S., making it the 29th coldest February in the 115-year record. For the second month in a row, Florida was the coldest state, relative to average. Florida had its 4th coldest February on record. Seven other states had February temperatures between 5th and 8th coldest on record: Louisiana, Texas, Alabama, Mississippi, Arkansas, Georgia, and South Carolina. Maine had its 3rd warmest February, New Hampshire its 5th, and Washington its 6th. Precipitation across the U.S. was near average in February.
Warmest and driest winter on record in Canada
Canada had its warmest winter on record, 4.0°C (7.2°F) above average, according to Environment Canada. The previous record was 3.9°C above average, set in 2005-2006. Canada also experienced its driest winter on record this year, with precipitation 22.0% below normal. The previous driest winter was 1977-1978 (20.1% below normal). Canadian weather records go back 63 years, to 1948. David Phillips, a senior climatologist with Environment Canada, warned of potential "horrific" water shortages, insect infestations, and wildfires this summer due to the warm, dry winter. Phillips blamed the warm winter weather on El Niño and the severe loss of arctic sea ice last fall. The winter season in Canada has warmed, on average, by 2.5°C (4.5°F) over the past 63 years.
Figure 2. Departure of temperature from average in Canada for the winter of 2009 - 2010. Image credit: Environment Canada.
Brazilian tropical/subtropical storm named "Anita"
The South Atlantic tropical/subtropical storm we've been tracking this week has moved over colder waters and has now transitioned to a regular extratropical storm. Earlier this week, the storm became just the 7th tropical or subtropical cyclone on record in the South Atlantic. According to a statement put out by MetSul Meteorologia, a Brazilian weather company, this storm is now named "Tropical Storm Anita:"
The regional weather centers and the private weather enterprises of both Rio Grande do Sul and Santa Catarina, southernmost Brazilian states, in a joint decision, named Anita the rare tropical storm of March 9th and 10th in the coastal areas of the region. The name was chosen considering a historic figure of Rio Grande do Sul and Santa Catarina, both states affected by the tropical cyclone. Anita Garibaldi (1821-1849) was a heroine of the Farroupilha Revolution (1835-1845), one of the most important events in the Brazilian history that took place in the Southern part of the country. Anita was used in the past to designate tropical cyclones in other basins: North Atlantic, the Pacific and the Indian Ocean.
Next week, we need to keep an eye on northeastern Australia, where Tropical Cyclone 20 may pay a visit. The storm is under light shear and warm waters, and is forecast to increase to Category 4 strength by Monday. Also of concern is Tropical Cyclone 19, which is expected to hit Fiji as a Category 2 storm early next week.
First tornado death of the year for the U.S
A tornado that hit Cleburne, Arkansas on Wednesday caused three serious injuries and the tornado season's first fatality, a 79-year old man sheltering in his single story wood-frame home. Yesterday, a suspected tornado ripped through Haines City, Florida destroying four condos and damaging fifteen others. One person was injured. Two other tornadoes caused minor damage in central Florida. The severe weather outbreak continues today, as NOAA's Storm Prediction Center is forecasting a "slight" chance of severe weather over portions of Florida, Georgia, Alabama, Kentucky, Indiana, and Ohio. After today, the severe weather action should diminish for at least five days over the U.S. The major U.S. weather story this weekend will be flooding in the Mid-Atlantic, where heavy rains of up to four inches are expected. Soils are already saturated and the heavy snows from this winter's major snowstorms will also melt, likely creating moderate flooding problems over much of the Mid-Atlantic.
Links to follow:
Interactive tornado map
Severe weather page
Figure 3. Severe weather forecast for today from the NOAA Storm Prediction Center.
Updated: 06:47 PM GMT vào 12 Tháng ba, 2010
By: JeffMasters, 03:09 PM GMT vào 11 Tháng ba, 2010
The unnamed South Atlantic tropical/subtropical cyclone (90Q) off the coast of Brazil continues to spin slowly out to sea, and is not a threat to any land areas. The storm, just the 7th tropical or subtropical cyclone on record in the South Atlantic, has a well-defined surface circulation, top wind speeds near minimum tropical storm force (40 mph), a surface pressure near 1004 mb, and a modest amount of heavy thunderstorm activity on its south side. Strong upper-level winds from the northeast are creating about 20 knots of wind shear over the storm, keeping the northeast side of the circulation exposed to view. Sea surface temperatures are about 25.5°C, which is about 1°C below what is typically needed to support a tropical storm. The storm is headed southeastward out to sea at about 10 mph, and will lose its tropical characteristics and get absorbed by a frontal system by Saturday.
Figure 1. Morning visible satellite image of the Brazilian unnamed tropical/subtropical storm.
When the storm formed two days ago, it began as a cold-cored system aloft, with a warm core at the surface, making it a hybrid subtropical storm. Yesterday, the entire core of the storm warmed enough for it to be worthy of consideration for tropical storm status. Tropical and subtropical storms are so rare in the South Atlantic that there is no official naming of depressions or storms done. The cyclone had top winds of at least 35 mph this morning at 7am EST as seen on an ASCAT pass, and satellite estimates of the storm's intensity have held steady at 40 mph (minimum subtropical storms strength) for the past 12 hours. ASCAT winds tend to be biased a little low at this speed range, so 40 mph--minimum tropical storm strength--is probably the best estimate of the winds. Phase space diagrams from Florida State University are showing that the storm has grown less tropical (warm-cored) in nature over the past 12 hours. When compared to similar systems that have developed in the North Atlantic that have been named, I definitely think today's storm deserves a name. The World Meteorological Organization should act to come up with a list of names for the South Atlantic, since these storms have the potential to cause considerable death and destruction along the South American coast, and deserve to receive the extra attention naming would provide.
South Atlantic tropical storm history
Brazil has had only one landfalling tropical cyclone in its history, Cyclone Catarina of March 2004. Catarina is one of only six known tropical or subtropical cyclones to form in the South Atlantic, and the only one to reach hurricane strength. Today's storm is probably the fourth strongest tropical/subtropical storm on record in the South Atlantic, behind Hurricane Catarina and an unnamed February 2006 storm that may have attained wind speeds of 65 mph, and a subtropical storm that brought heavy flooding to the coast of Uruguay in January 2009.. Tropical cyclones rarely form in the South Atlantic Ocean, due to strong upper-level wind shear, cool water temperatures, and the lack of an initial disturbance to get things spinning (no African waves or Intertropical Convergence Zone exist in the proper locations in the South Atlantic to help spawn tropical storms). Today's storm is located close to where Catarina formed.
Climate change and South Atlantic storms
It is uncertain whether climate change may cause an increase in South Atlantic tropical storms in the future. While today's storm formed over waters that were about 1°C above average in temperature, Catarina in 2004 formed over waters that were 0.5°C cooler than average. Sea surface temperature is not the main limiting factor inhibiting these storms, wind shear is. How climate change might change wind shear over South America has not been well-studied.
Tornadoes rip Arkansas, Louisiana
It's March, and that means we can expect severe weather. Last night, one tornado was reported in Louisiana and four in Arkansas, in association with a powerful low pressure system tracking slowly across the nation's midsection. The most damaging tornado hit Cleburne, Arkansas, destroying several houses and blowing down trees and power lines. Three serious injuries were reported. The storms also dropped baseball-sized hail near Plain Dealing and Texarkana, Arkansas. The severe weather has pushed east, and NOAA's Storm Prediction Center is forecasting a "slight" chance of severe weather over Florida today, plus portions of Louisiana, Mississippi, and Alabama.
Links to follow:
Interactive tornado map
Severe weather page
Figure 2. Severe weather forecast for today from the NOAA Storm Prediction Center.
Updated: 06:25 PM GMT vào 11 Tháng ba, 2010
By: JeffMasters, 02:10 PM GMT vào 10 Tháng ba, 2010
A rare weather event is underway in the South Atlantic Ocean, where the basin's 7th recorded tropical or subtropical cyclone of all-time has formed. An area of disturbed weather (Invest 90Q) off the coast of Brazil, near 30S 48W, attained a well-defined surface circulation, top wind speeds of tropical depression strength (35 mph), a warm core in the bottom portion of the atmosphere, and a cold core aloft last night. If this storm had been in the North Atlantic, there is a good chance it would have been named Subtropical Depression One. However, tropical and subtropical storms are so rare in the South Atlantic that there is no official naming of depressions or storms done. The cyclone had top winds of at least 35 mph as seen on an ASCAT pass at 7:02 am EST this morning (Figure 2), and satellite estimates of the storm's intensity topped out at 40 mph (minimum subtropical storms strength) last night. This morning, the satellite estimates are showing that the system has weakened to a 35 mph tropical depression. There is some moderate wind shear interfering with development, and sea surface temperatures are about 25°C, which is about 1°C below what is typically needed to support a tropical storm. The storm is headed eastward out to sea, and is not a threat to any land areas. The models show the storm will lose its tropical characteristics and get absorbed by a frontal system by Saturday.
Figure 1. Afternoon visible satellite image of the Brazilian Invest 90Q.
Figure 2. Satellite-measured winds from ASCAT clearly show the circulation of the cyclone in this pass from 7:02 am EST on March 10, 2010. Top winds as seen be ASCAT were 30 knots (35 mph), just below the 40 mph needed for it to be a tropical storm. Image credit: NOAA/NESDIS/ORA.
Brazil has had only one landfalling tropical cyclone in its history, Cyclone Catarina of March 2004. Catarina is one of only six known tropical or subtropical cyclones to form in the South Atlantic, and the only one to reach hurricane strength. Tropical cyclones rarely form in the South Atlantic Ocean, due to strong upper-level wind shear, cool water temperatures, and the lack of an initial disturbance to get things spinning (no African waves or Intertropical Convergence Zone exist in the proper locations in the South Atlantic to help spawn tropical storms). Today's storm is located close to where Catarina formed.
Severe weather season begins
It's March, and that means severe weather season will get underway in earnest for the Midwest U.S., and powerful spring storm systems draw warm, moist air from the Gulf of Mexico northward, to collide with cold, dry air from Canada. It's been a quiet early season, with only 42 tornadoes reported thus far this year (as of Sunday), compared to a normal 70 - 100 twisters. There was only one tornado in the U.S. in February, in a San Joaquin Valley oilfield in California two weekends ago. A year ago, there were 36 February tornadoes, and the year's deadliest tornado occurred on Feb. 10, 2009, in Lone Grove, Oklahoma, where eight people died in a storm with winds estimated at 170 mph. But thanks to a very wet winter and a continued active jet stream pattern that will pull strong storms through the Midwestern U.S. this month, expect at least an average March for severe weather. NOAA's Storm Prediction Center is forecasting a "slight" chance of severe weather across a large portion of the Mississippi Valley today, in association with a strong cold front that will be plowing through the region. Strong thuderstorms capable of generating damaging winds and large hail should develop along the front from southeast Kansas through eastern Oklahoma into NE Texas by middle/late afternoon. The storms should consolidate into broken bands and move into Missouri and and Arkansas by early evening. Isolated tornadoes are also possible in the entire "slight" risk area.
Figure 3. Severe weather forecast for today from the NOAA Storm Prediction Center.
Hurricane Hugo talk
I'm presenting a talk to a class at the University of Michigan this morning on my 1989 flight through Hurricane Hugo. You can listen in live starting at about 10:10 - 10:15 am EST by pointing your browser to http://samson.lecturetools.org/. You'll need to have Apple Quicktime installed. If all goes well, the talk will be recorded and you can view it later, as well.
Updated: 08:45 PM GMT vào 10 Tháng ba, 2010
By: JeffMasters, 04:52 PM GMT vào 08 Tháng ba, 2010
Sea Surface Temperatures (SSTs) in the Atlantic's Main Development Region for hurricanes were at their highest February level on record last month, according to an analysis of historical SST data from the UK Hadley Center. SST data goes back to 1850, though there is much missing data before 1910 and during WWI and WWII. The region between 10°N and 20°N, between the coast of Africa and Central America, is called the Main Development Region (MDR) because virtually all African waves originate in this region. These African waves account for 85% of all Atlantic major hurricanes and 60% of all named storms. When SSTs in the MDR are much above average during hurricane season, a very active season typically results (if there is no El Niño event present.)
Figure 1. The departure of sea surface temperature (SST) from average for March 7, 2010, as derived from the AMSR and AVHRR satellite data. Image credit: NOAA.
SSTs in the Main Development Region (10°N to 20°N and 20°W to 85°W) were an eye-opening 1.02°C above average during February. This easily beats the previous record of 0.83°C set in 1998. SSTs in the Main Development Region are already warmer than they were during June of last year, which is pretty remarkable, considering February is usually the coldest month of the year for SSTs in the North Atlantic. The 1.02°C anomaly is the 6th highest monthly SST anomaly for the MDR on record. The only other months with higher anomalies all occurred during 2005 (April, May, June, July, and September 2005 had anomalies of 1.06°C - 1.23°C).
What is responsible for the high SSTs?
Don't blame El Niño for the high Atlantic SSTs. El Niño is a warming of the Pacific waters near the Equator, and has no direct impact on Atlantic SSTs. Instead, blame the Arctic Oscillation (AO) or its close cousin, the North Atlantic Oscillation (NAO). The AO and NAO are climate patterns in the North Atlantic Ocean related to fluctuations in the difference of sea-level pressure between the Icelandic Low and the Azores-Bermuda High. They are some of the oldest known climate oscillations; seafaring Scandinavians described the pattern several centuries ago. Through east-west oscillation motions of the Icelandic Low and the Azores-Bermuda High, the AO/NAO controls the strength and direction of westerly winds and storm tracks across the North Atlantic. A large difference in the pressure between Iceland and the Azores (positive NAO) leads to increased westerly winds and mild and wet winters in Europe. Positive NAO conditions also cause the Icelandic Low to draw a stronger south-westerly flow of air over eastern North America, preventing Arctic air from plunging southward. In contrast, if the difference in sea-level pressure between Iceland and the Azores is small (negative NAO), westerly winds are suppressed, allowing Arctic air to spill southwards into eastern North America more readily. The winter of 2009 - 2010 has seen the most negative AO and NAO patterns since record keeping began in 1950, which caused a very cold winter in Florida and surrounding states. A negative AO/NAO implies a very weak Azores-Bermuda High, which reduces the trade winds circulating around the High. During December - February, trade winds between Africa and the Lesser Antilles Islands in the hurricane Main Development Region were 1 - 2 m/s (2.2 - 4.5 mph) below average (Figure 2). Slower trade winds mean less mixing of the surface waters with cooler waters down deep, plus less evaporational cooling of the surface water. As a result, the ocean has heated up significantly, relative to normal, over the winter. This heating is superimposed on the very warm global SSTs we've been seeing over the past decade, leading to the current record warmth. Global and Northern Hemisphere SSTs were the 2nd warmest on record in both December and January.
Figure 2. Sea level pressure averaged for the period December 2009 - February 2010 (left) and the sea level pressure averaged for the period December - February from the long-term mean (1968 - 1998). This winter, the Azores-Bermuda High was about 3 - 4 mb weaker than in a typical winter, due to strongly negative AO/NAO conditions. Image credit: NOAA/ESRL.
Figure 3. Departure of surface wind speed from average for December 2009 - February 2010. Winds were about 1 - 2 m/s (2.2 - 4.5 mph) lower than average over the Atlantic hurricane Main Development Region (MDR). Image credit: NOAA/ESRL.
What does this imply for the coming hurricane season?
According to Dr. Phil Klotzbach of the University of Colorado, February temperatures in the MDR are not strongly correlated with active hurricane seasons. The mathematical correlation between hurricane season Accumulated Cyclone Energy (ACE) and February SSTs is only 0.26, which is considered weak. Past hurricane seasons that had high February SST anomalies include 1998 (0.83°C anomaly), 2007 (0.71°C anomaly), and 1958 (0.68°C anomaly). These three years averaged 13 named storms, 8 hurricanes, and 3 intense hurricanes, which is considerably higher than the average of 10, 6, and 2. The big question is, how long will the strong negative AO/NAO conditions keep the Azores-Bermuda High weak? Well, the AO has risen to near-neutral values over the past week, and the latest 2-week forecast from the GFS model show that the AO and NAO will not be as strongly negative during March. This should allow the Azores-Bermuda High to strengthen some this month and increase the trade winds over the MDR. However, I still expect we'll set a record for warmest-ever March SSTs in the Main Development Region. Longer term, the crystal ball is very fuzzy, as our ability to predict the weather months in advance is poor. The long-range NOAA CFS model is predicting SSTs in the Atlantic MDR will be about 0.70°C above average during the peak months of hurricane season, making it one of the top five warmest years on record--but not as warm as the unbelievable Hurricane Season of 2005, which averaged 0.95°C above normal during August - October. The other big question is, when will El Niño fade? El Niño is currently holding steady at moderate intensity, and I expect that will continue through at least mid-April. It is possible El Niño will linger long enough into the year that it will create increased wind shear that will suppress this year's hurricane season.
An area of disturbed weather off the coast of Brazil, near 24S 36W, has changed little over the past two days. This disturbance still has a slight potential to develop into subtropical or tropical depression by Wednesday, according to the latest runs of the ECMWF, GFS, and NOGAPS models. Satellite imagery shows little organization to the cloud pattern, and only limited heavy thunderstorm activity. Wind shear over the region is about 20 knots, which is rather high, and should keep any development slow. Sea surface temperatures are about 27°C, about 1°C above average, which is warm enough to support a tropical storm. The system is small, limiting its potential to become a tropical cyclone. I don't think it will become a subtropical depression.
I'll have a new post on Wednesday.
Updated: 02:59 PM GMT vào 18 Tháng tám, 2011
By: JeffMasters, 03:05 PM GMT vào 06 Tháng ba, 2010
An area of disturbed weather off the coast of Brazil, near 17S 38W, has changed little over the past day. It has a slight potential to develop into subtropical or tropical depression early next week. Satellite winds estimates from the WindSat instrument show an elongated area of converging winds, but no organized surface circulation. Satellite loops show little organization to the cloud pattern, and only limited heavy thunderstorm activity. Wind shear over the region is about 20 knots, which is rather high, and should keep any development slow. Sea surface temperatures are about 28°C, about 1°C above average, and plenty warm enough to support a tropical storm. The system is small, and this will limit its potential to become a tropical cyclone.
Figure 1. Morning visible satellite image of the Brazilian disturbance.
The ECMWF, UKMET, and NOGAPS models have backed off on their predictions of development a fair amount in recent runs. Phase space diagrams from Florida State University show that this storm has less of a warm core than before, meaning it would probably be classifiable as a subtropical storm if it gets more organized and achieves surface wind speeds of at least 39 mph. The system does not appear to be a threat to bring heavy rains to the Brazilian coast. I give this storm a low (< 30% chance) of developing into a tropical or subtropical depression by Monday. The storm should move to the south or southeast away from the coast. Only six known tropical or subtropical cyclones have formed in the South Atlantic. Tropical cyclones rarely form in the South Atlantic Ocean due to strong upper-level wind shear, cool water temperatures, and the lack of an initial disturbance to get things spinning (no African waves or Intertropical Convergence Zone exist in the proper locations in the South Atlantic to help spawn tropical storms).
Portlight continues relief efforts in Haiti
Portlight and the Liberty Schooner are sponsoring "The Haitian Food Voyage," shipping 10,000 pounds of rice to Haiti. Thanks to your generous donations, the mission is set to sail to Haiti during the second week of April. Please visit the Portlight.org blog to learn more and to donate to this worthy cause.
Figure 2. R.Richard Lumarque, Portlight's on-site coordinator in Haiti, assists a woman who has just received a new walker from Portlight. The woman was injured when a 3-story building collapsed on her during the January earthquake.
Updated: 03:07 PM GMT vào 06 Tháng ba, 2010
By: JeffMasters, 03:15 PM GMT vào 05 Tháng ba, 2010
An area of disturbed weather has formed off the coast of Brazil, near 18S 38W. This disturbance has the potential to develop into subtropical or tropical depression early next week. Satellite winds estimates from the WindSat instrument show an elongated area of converging winds, but no organized surface circulation. Satellite loops show little organization to the cloud pattern, and only limited heavy thunderstorm activity. Wind shear over the region is about 20 knots, which is rather high, and should keep any development slow. Sea surface temperatures are about 28°C, about 1°C above average, and plenty warm enough to support a tropical storm.
Figure 1. Morning visible satellite image of the Brazilian disturbance.
Several global models, such as the ECMWF, UKMET, and NOGAPS models have been developing this system in recent runs. Phase space diagrams form Florida State University confirm that this storm is expected to primarily be a warm-cored system, meaning it will probably be classifiable as a subtropical or tropical storm if it attains surface wind speeds of at least 39 mph. The system is capable of bringing heavy rains to the Brazilian coast while it is in its formative stages over the next few days, but I doubt that these rains would be heavy enough to cause flooding concerns. By Monday, the storm should be headed southwards or south-eastwards out to sea, and it appears unlikely that Brazil would see tropical storm-force winds of 39+ mph from this system. I give this storm a low (< 30% chance) of developing into a tropical or subtropical depression by Sunday.
Figure 2. The MODIS instrument on-board NASA's Aqua satellite captured this true-color image of a rare tropical cyclone in the South Atlantic ocean just off the coast of Santa Catarina and Rio Grande do Sul, Brazil's southernmost states. The National Hurricane Center in Miami estimated the storm was a full-fledged, Category I hurricane with central winds between 75 mph and 80 mph (121 kph to 129 kph), making it the first hurricane in the South Atlantic in recorded history.
Comparisons to Cyclone Catarina
Brazil has had only one landfalling tropical cyclone in its history, Cyclone Catarina of March 2004. Catarina is one of only six known tropical or subtropical cyclones to form in the South Atlantic, and the only one to reach hurricane strength. Tropical cyclones rarely form in the South Atlantic Ocean, due to strong upper-level wind shear, cool water temperatures, and the lack of an initial disturbance to get things spinning (no African waves or Intertropical Convergence Zone exist in the proper locations in the South Atlantic to help spawn tropical storms). Today's disturbance is located much closer to the Equator than where Catarina formed. Thus, it has warmer waters to work with, and potentially less wind shear.
I'll probably do a quick update this weekend.
By: JeffMasters, 02:43 PM GMT vào 03 Tháng ba, 2010
When Winter Storm Xynthia powered ashore over Europe last weekend, it brought hurricane-force wind gusts, flooding rains, and a 1-meter storm surge topped by 8-meter high battering waves that overwhelmed sea walls in France, killing scores of people. Today, AIR Worldwide estimated the insured damage from the storm at $1.5 - $3 billion. Intense extratropical cyclones like Xynthia, with central pressures below 970 mb, make up less than 20% of all wintertime cyclones in the Northern Hemisphere, but cause the vast majority of the devastation and loss of life. The ten deadliest winter storms to hit Europe over the past 60 years all had minimum pressures lower than 970 mb. The situation is similar for North America, though the storms generally do not get as intense as their European counterparts (the four major Nor'easters this winter have had central pressures of 968, 969, 978, and 972 mb). It is important, then, to ask if these strongest of the strong storms are changing in frequency, and whether a future warmer world will have more or less of these storms.
Figure 1. Winter Storm Xynthia, as captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite. Image was acquired in two separate overpasses on February 27, 2010. MODIS captured the eastern half of the image around 10:50 UTC, and the western half about 12:30 UTC. Forming a giant comma shape, clouds stretch from the Atlantic Ocean to northern Italy. Xynthia peaked in intensity at 18 UTC February 27, with a central pressure of 966 mb. Image credit: NASA.
Have intense Northern Hemisphere winter storms increased in number?
Most of the material for this post comes from three sources: the 2007 IPCC report, a 2009 review titled, Extra-tropical cyclones in the present and future climate: a review, and Weather and Climate Extremes in a Changing Climate, a 2009 report from the U.S. Global Change Research Program (USGCRP). An increasing number of intense winter storms in some regions of the Northern Hemisphere over the last few decades of the 20th century was a common theme of many of the studies reviewed. However, the studies used different measures as to what constitutes an "intense" storm, and have some disagreement on which areas of the globe are seeing more intense storms. A 1996 study by Canadian researcher Steven Lambert (Figure 3) found a marked increase in intense wintertime cyclones (central pressure less than 970 mb) in the latter part of the 20th century. Most of this increase occurred in the Pacific Ocean. Other studies (Geng and Sugi, 2001, and Paciorek et al., 2002) found an increase in intense winter storms over both the North Atlantic and North Pacific in the latter part of the 20th century. Benestad and Chen(2006) found an increase in the number of intense storms over the Nordic countries over the period 1955-1994, but no trend in the western parts of the North Atlantic. Gulev et al. (2001) found a small increase in the number of intense North Pacific storms (core pressure below 980 mb), a large increase in the Arctic, but a small decrease in the Atlantic. McCabe et al. 2001 found an increase at both mid-latitudes and high latitudes, particularly in the Arctic. Hirsch et al. (2001) found that the number of intense Nor'easters along the U.S. East Coast (storms with winds > 52 mph) stayed roughly constant at three storms per year over the period 1951 - 1997. Over the period 1900 to 1990, the number of strong cyclones (less than 992 mb) in November and December more than doubled over the Great Lakes of North America (Angel and Isard, 1998). With regards to Europe, Lionello et al. conclude, "the bulk of evidence from recent studies mostly supports, or at least does not contradict, the finding of an attenuation of cyclones over the Mediterranean and an intensification over Northern Europe during the second part of the twentieth century".
Figure 2. Trends in strong extratropical cyclones with central pressures less than 980 mb, for the period 1989 - 2009, as estimated using thirteen different methods, M02 - M22, defined in Neu et al., 2012. The error-bars represent the 95% confidence range of the trend estimate. A trend is significant at 5% level if the error-bar does not include zero. Four of the thirteen methods showed a slightly significant downward trend in both summertime and wintertime Northern Hemisphere strong extratropical cyclones during the period. None of the methods showed a statistically significant trend in Southern Hemisphere strong extratropical cyclones during either summer or winter. Image credit: U. Neu, M.G. Akperov, N. Bellenbaum, R. Benestad, R. Blender, R. Caballero, A. Cocozza, H.F. Dacre, Y. Feng, K. Fraedrich, J. Grieger, S. Gulev, J. Hanley, T. Hewson, M. Inatsu, K. Keay, S.F. Kew, I. Kindem, G.C. Leckebusch, M.L.R. Liberato, P. Lionello, I.I. Mokhov, J.G. Pinto, C.C. Raible, M. Reale, I. Rudeva, M. Schuster, I. Simmonds, M. Sinclair, M. Sprenger, N.D. Tilinina, I.F. Trigo, S. Ulbrich, U. Ulbrich, X.L. Wang, and H. Wernli, "IMILAST – a community effort to intercompare extratropical cyclone detection and tracking algorithms: assessing method-related uncertainties", Bulletin of the American Meteorological Society, pp. 120919072158001, 2012. http://dx.doi.org/10.1175/BAMS-D-11-00154.1
In summary, the best science we have shows that there has not been a statistically significant increase in the number of intense wintertime extratropical storms globally in the past two decades, but there has been and increase in the North Pacific and Arctic. Increased wave heights have been observed along the coasts of Oregon and Washington during this period, adding confidence to the finding of increased intense storm activity. The evidence for an observed increase in intense wintertime cyclones in the North Atlantic is uncertain. In particular, intense Nor'easters affecting the Northeast U.S. showed no increase in number over the latter part of the 20th century. This analysis is supported by the fact that wintertime wave heights recorded since the mid-1970s by the three buoys along the central U.S. Atlantic coast have shown little change (Komar and Allan, 2007a,b, 2008). However, even though Nor'easters have not been getting stronger, they have been dropping more precipitation, in the form of both rain and snow. Wintertime top 5% heavy precipitation events (both rain and snow) have increased over the Northeast U.S. in recent decades (Groisman et al., 2004), so Nor'easters have been more of a threat to cause flooding problems and heavy snow events. In all portions of the globe, tracks of extratropical storms have shifted poleward in recent decades, in accordance with global warming theory. Note that the historical data base for strong winter storms is in better shape than the data base we are using to try to detect long-term changes in hurricanes. The Ulbrich et al. (2009) review article states:
The IPCC AR4 (cf. Trenberth et al. 2007, p. 312) states that the detection of long-term changes in cyclone measures is hampered by incomplete and changing observing systems. Recent studies found, however, a general reliability of results for cyclones in the Northern Hemisphere. There are no sudden shifts in intensities that would indicate inhomogeneities, and also a comparison with cyclone activity estimated from regional surface and radiosonde data (Wang et al. 2006b; Harnik and Chang 2003) confirmed the general reliability of the data".
However, the data is not as good in the Southern Hemisphere, so the finding that intense winter storms are also increasing in that hemisphere must be viewed with caution.
Figure 3. Number of intense winter cyclones with central pressure less than 970 mb in the Northern Hemisphere, North Pacific, and North Atlantic between 1899 - 1991. Image credit: Lambert, S.J., 1996: Intense extratropical Northern Hemisphere winter cyclone events: 1899-1991. J. Geophys. Res., 101D, 2131921325.
Intense winter storms may increase in number
General Circulation Models (GCMs) like the ones used in the 2007 IPCC Assessment Report do a very good job simulating how winter storms behave in the current climate, and we can run simulations of the atmosphere with extra greenhouse gases to see how winter storms will behave in the future. The results are very interesting. Global warming is expected to warm the poles more than the equatorial regions. This reduces the difference in temperature between the pole and Equator. Since winter storms form in response to the atmosphere's need to transport heat from the Equator to the poles, this reduced temperature difference reduces the need for winter storms, and thus the models predict fewer storms will form. However, since a warmer world increases the amount of evaporation from the surface and puts more moisture in the air, these future storms drop more precipitation. During the process of creating that precipitation, the water vapor in the storm must condense into liquid or frozen water, liberating "latent heat"--the extra heat that was originally added to the water vapor to evaporate it in the first place. This latent heat intensifies the winter storm, lowering the central pressure and making the winds increase. So, the modeling studies predict a future with fewer total winter storms, but a greater number of intense storms. These intense storms will have more lift, and will thus tend to drop more precipitation--including snow, when we get areas of strong lift in the -15°C preferred snowflake formation region. For completeness' sake, some of the studies that show more intense winter cyclones in a warmer world are Lambert (1995), Boer et al. (1992), Dai et al. (2001), Geng and Sugi (2003), Fyfe (2003), Lambert (2004), Leckebusch and Ulbrich (2004), Lambert and Fyfe (2006), Pinto et al. (2007), and Lionello et al. (2008). A review article be Ulbrich et al. provides a nice summary. However, two studies--Pinto et al. (2007) and Bengtsson et al. 2006--suggest that the more intense winter cyclones will affect only certain preferred regions, namely northwestern Europe and Alaska's Aleutian Islands. At least three other studies also find that northwestern Europe--including the British Isles, the Netherlands, northern France, northern Germany, Denmark and Norway--can expect a significant increase in intense wintertime cyclones in a future warmer world (Lionello et al., 2008; Leckebusch and Ulbrich 2004; and Leckebusch et al., 2006). None of these studies showed a significant increase in the number of intense Nor'easters affecting the Northeast U.S. One interesting new study (O'Gorman, 2010) found that wintertime extratropical cyclones in the northern hemisphere would increase in intensity by 2100 primarily because the surface would heat up more than the upper air, making the atmosphere more unstable. In summer, the models predict a decrease in extratropical cyclones in the Northern Hemisphere. In the Southern Hemisphere, these storms were predicted in increase in intensity year-round. The models studied were the 2007 IPCC suite of climate models.
What the IPCC models say
The Lambert and Fyfe (2006) study, titled, "Changes in winter cyclone frequencies and strengths simulated in enhanced greenhouse warming experiments: results from the models participating in the IPCC diagnostic exercise", looked at thirteen models used to formulate the 2007 IPCC Climate Change report. Of these models, eleven simulated an increase in the number and intensity of the most intense cyclones (<970 mb pressure) in the climate expected by 2100. Two of the models did not, so it is fair to say that there is some uncertainty in these results. Nevertheless, the model results are compelling enough that the U.S. Global Change Research Program (USGCRP), a scientific advisory board created by the President and Congress, concluded this in their 2009 U.S. Climate Impacts Report: "Cold-season storm tracks are shifting northward and the strongest storms are likely to become stronger and more frequent". The USGRP concluded that an increase of between four and twelve intense wintertime extratropical storms per year could be expected over the Northern Hemisphere by 2100, depending upon the amount of greenhouse gases put into the air (Figure 3). If we assume that the current climate is producing the same number of intense winter storms as it did over the period 1961-2000--about 53--this represents an increase of between 8% and 23% in intense wintertime extratropical storms.
Figure 4. The projected change in intense wintertime extratropical storms with central pressures < 970 mb for the Northern Hemisphere under various emission scenarios. Storms counted occur poleward of 30°N during the 120-day season beginning November 15. A future with relatively low emissions of greenhouse gases (B1 scenario, blue line) is expected to result in an additional four intense extratropical storms per year, while up to twelve additional intense storms per year can be expected in a future with high emissions (red and black lines). Humanity is currently on a high emissions track. Figure was adapted from Lambert and Fyfe (2006), and was taken from Weather and Climate Extremes in a Changing Climate, a 2009 report from the the U.S. Global Change Research Program (USGCRP). The USGRP began as a presidential initiative in 1989 and was mandated by Congress in the Global Change Research Act of 1990, which called for "a comprehensive and integrated United States research program which will assist the Nation and the world to understand, assess, predict, and respond to human-induced and natural processes of global change".
The best science we have suggests that there has not been an increase in intense wintertime extratropical cyclones globally in recent decades, though there has been an increase in the Pacific and Arctic. Research by Barredo (2010) suggests that Europe has not yet seen a significant increase in damaging winter storms, since normalized damages from severe winter storms did not increase between 1970 - 2008. The 2013 IPCC report sums it up this way:
"Confidence in large scale changes in the intensity of extreme extratropical cyclones since 1900 is low. There is also low confidence for a clear trend in storminess proxies over the last century due to inconsistencies between studies or lack of long-term data in some parts of the world (particularly in the SH). Likewise, confidence in trends in extreme winds is low, due to quality and consistency issues with analyzed data."
The report says that extratropical cyclones are expected to shift poleward in a warming climate, but does not have any conclusions on how the most intense storms may change, other than to dump more precipitation.
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Heavy snowfall in a warming world
A rare Deep South snow event breaks Dallas' all-time snowfall record, where I point out that more heavy snowstorms occur in warmer-than-average years.
Updated: 02:41 PM GMT vào 13 Tháng ba, 2014
By: JeffMasters, 04:21 PM GMT vào 01 Tháng ba, 2010
Devastating Winter Storm Xynthia ripped a swath of destruction through Portugal, Spain, France, Belgium, and Germany over the weekend, killing at least 62 people. It was Europe's 5th deadliest winter storm of the past 60 years. Hardest hit was France, where at least 51 died. The storm also caused six deaths in Germany, including a 2-year-old boy blown into a river and drowned. Three people were dead in Spain, and Belgium, Portugal, and England had one fatality each. At least ten people are still missing. Most of the deaths in France occurred when a powerful storm surge topped by battering waves up to 25 feet high, hitting at high tide, smashed though the sea wall off the coastal town of L'Aiguillon-sur-Mer. A mobile home park built close to the sea wall was particularly hard-hit. The sea wall was several hundred years old, built in the time of Napoleon, and locating a mobile home park so close to it showed poor coastal development practices, critics said. The storm cut power to more than 1 million homes in France, and up to 1 million customers in Portugal also lost power. A few wind peak wind gusts measured during the storm:
Pampilhosa da Serra 147 km/h (91 mph)
Penhas Douradas 126.1 km/h (78 mph)
Porto (Airport LPPR) 113km/h (70 mph)
Lardeira: 196.1 km/h (122 mph)
Serra do Eixe: 157 km/h (98 mph)
Campus de Vigo: 146.9 km/h (92 mph)
Gandara: 145.8 km/h (91 mph)
Eiffel Tower, Paris: 175 km/h (106 mph)
Saint-Clement of the Whales: 159km/h (99 mph)
Charente-Maritime: 161km/h (100 mph)
A Personal Weather Station in Les Portes-en-Re recorded sustained winds of 143 km/h (89 mph) gusting to 180 km/h (112 mph) before losing power at the height of the storm. According to Meteo France, the maximum recorded gust from Xynthia for elevations lower than 1200m was 160 km/h along the coast and 120 km/h inland. In 1999, Winter Storm Lothar brought gusts of almost 200 km/h to coastal areas and up to 160 km/h in the interior at these lower elevations.
Figure 1. Six-hour animation of the surface winds as Winter Storm Xynthia crossed the Bay of Biscay and smashed into France.
Destructive European storms of the past 60 years:
2010: Winter Storm Xynthia of February 27, 2010 killed 51 people in France, Spain, and neighboring countries, and did $2 - $4 billion in damage. Lowest pressure: 967 mb.
Winter Storm Klaus hit northern Spain and southwest France January 23 - 25, 2009, and was Earth's most costly natural disaster of 2009, causing $5.1 billion in damage and killing 26. Minimum pressure: 967 mb.
Kyrill (January 18, 2007) killed at least 45, with Germany suffering the most fatalities (13). Minimum pressure: 964 mb.
Back-to-back winter storms Lothar and Martin December 26-28, 1999) killed 140 people, 88 of the victims in France. Minimum pressure: 961 mb (Lothar), 965 mb (Martin).
The Burns' Day Storm of 1990 killed 97, mostly in England. Minimum pressure: 949 mb.
The Great Storm of 1987 was Europe's "storm of the century". It killed 22 people in England and France. Minimum pressure: 953 mb.
The North Sea Flood of 1962 killed 318 people--315 of them in Hamburg, Germany.
The North Sea Flood of 1953 killed 2,000 people in the Netherlands and England.
Xynthia's warm air surge sets records
One reason Xynthia became so powerful is that it formed very far south, where it was able to tap into an airmass that was unusually warm and moist. Satellite measurements (Figure 2) showed a plume of high total precipitable water (the amount of precipitation one can produce by condensing all the water vapor from the surface to the top of the atmosphere), about 300% above average, flowing from southwest to northeast along Xynthia's cold front. Enhancing the amount of moisture was the presence of very warm sea surface temperatures 1°C above average along this plume. As this extra moisture flowed into the storm, the moisture condensed into rain, releasing the "latent heat" stored up in the water vapor (the extra energy that was originally used to evaporate the water into water vapor). This latent heat further intensified Xynthia. The storm's central pressure fell to 966 mb at the storm's peak intensity, reached at 18 GMT Saturday after it passed over Spain's northwest corner.
As warm, tropical air surged northeastwards in advance of Xynthia's cold front, it set several all-time high temperature records for the month of February. Melilla, Spain hit 34°C (93°F) at 3pm local time on the 27th, beating previous highest February temperature of 30.6°C, set in 1979. The temperature surged upwards a remarkable 9.1°C (16°F) in one hour as Xynthia's warm front passed through. Record February warmth was also observed in the Canary Islands as Xynthia's warm front passed though.
Figure 2. Satellite measurements show a region of high total precipitable water (the amount of precipitation one can produce by condensing all the water vapor from the surface to the top of the atmosphere) up to 300% above average, flowing from southwest to northeast along Xynthia's cold front. Enhancing the amount of moisture was the presence of very warm sea surface temperatures along this plume, about 1°C above average. If this pool of very warm water is still around in July, it could lead to an earlier than average start to the Atlantic hurricane season. Image credit: Sheldon Kusselson, NOAA/NESDIS, and National Hurricane Center.
For the the U.S., the next winter storm of note is a moderately strong low pressure system currently over Texas that is expected to move quickly eastwards today and Tuesday. The storm should bring an inch or so of snow to Atlanta and northeast Alabama, and 2 - 4" to the nearby mountains of South and North Carolina, including Charlotte. After that, the models show a long break from winter storm activity for the Eastern U.S. Beginning Sunday, it looks like it will be the Midwest's turn, when a powerful winter storm will drop out of the Rockies, then move across the northern tier of Midwestern states early next week.
I'll have a new post Tuesday or Wednesday.
Updated: 06:56 PM GMT vào 30 Tháng mười một, 2011
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.
Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather
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