Warm U.S. West, cold East: 4,000-year pattern Climatic change would bring more curvy jet streams throughout winter

These maps show winter temperature designs (top) and winter precipitation designs (bottom) connected having a curvy jet stream (not proven) that moves north in the Off-shore towards the Yukon and Alaska, then falls lower within the Canadian flatlands and in to the eastern U . s . States. A College of Utah-brought study implies that beginning 4,000 years back, the jet stream tended being curvier of computer was between 8,000 and 4,000 years back, and indicates climatic change will enhance such curviness and therefore frigid weather within the eastern states such as this past winter's. The curvy jet stream introduced abnormally warm temps (red-colored and orange) towards the West and Alaska as well as an abnormal frost nova (blue) towards the East earlier this winter, similar to what's proven within the top map, except top of the Area was cooler than proven. The underside map of the curvy jet stream precipitation pattern shows how that normally brings dry winters to red-orange areas and wet winters to blue regions. Precipitation designs this winter matched up the underside map in lots of regions, except California was drier than expected and also the upper Area was wetter than expected.Credit: Zhongfang Liu, Tianjin Normal College, China. Last winter's curvy jet stream pattern introduced mild temps to western The United States and harsh cold towards the East. A College of Utah-brought study implies that pattern grew to become more pronounced 4,000 years back, and indicates it might worsen as Earth's climate warms up.

"If the trend continues, it might lead to more extreme winter months occasions in The United States, as experienced this season with warm conditions in California and Alaska and invasion of cold Arctic air over the eastern USA," states geochemist Gabe Bowen, senior author from the study.

The research was released online April 16 through the journal Character Communications.

"A sinuous or curvy winter jet stream means unusual warmth in the western world, drought conditions simply from the West, and abnormally cold winters within the East and Southeast," adds Bowen, an connect professor of geology and geophysics in the College of Utah. "We had among extreme winter season climate that largely fit that pattern earlier this winter," although within the typical pattern California frequently is wetter.

It's not new for researchers to forecast the current warming of Earth's climate because of co2, methane along with other "green house" gases already has brought to elevated weather extremes and continuously achieve this.

The brand new study shows the jet stream pattern which brings United States winter season weather extremes is millennia old -- "a historical and chronic pattern of climate variability," Bowen states. Yet additionally, it indicates climatic change may boost the pattern so you will see more frequent or even more severe winter months extremes or both.

"This really is one other reason why we might convey more winter extremes in The United States, in addition to something of the model for which individuals extremes may seem like,Inch Bowen states. Human-triggered global warming is reducing equator-to-pole temperature variations the climate is warming more in the rods than in the equator. According to what went down in past millennia, that may create a curvy jet stream much more frequent and-or intense than now, he states.

Bowen and the co-authors examined formerly released data on oxygen isotope ratios in lake sediment cores and cave deposits from sites within the eastern and western U . s . States and Canada. Individuals isotopes were deposited in ancient rain fall and integrated into calcium carbonate. They deomonstrate jet stream directions throughout yesteryear 8,000 years, a geological time referred to as middle and late stages from the Holocene Epoch.

Next, the scientists did computer modeling or simulations of jet stream designs -- both curvy and much more direct west to east -- to exhibit how alterations in individuals designs can explain alterations in the isotope ratios left by rain fall within the old lake and cave deposits.

They discovered that the jet stream pattern -Known technically because the Off-shore United States teleconnection -- moved to some generally more "positive phase" -- meaning a curvy jet stream -- on the 500-year period beginning about 4,000 years back. Additionally for this millennial-scale alternation in jet stream designs, additionally they noted a cycle by which increases within the sun's intensity every two centuries result in the jet stream flatter.

Bowen carried out the research with Zhongfang Liu of Tianjin Normal College in China, Kei Yoshimura from the College of Tokyo, japan, Nikolaus Buenning from the College of Los Angeles, Camille Risi from the French National Center for Research, Jeffrey Welker from the College of Alaska at Anchorage, and Fasong Yuan of Cleveland Condition College.

The research was funded through the National Science Foundation, National Natural Science First step toward China, Japan Society for that Promotion of Science along with a joint program through the society and Japan's Secretary of state for Education, Culture, Sports, Science: this program for Risk Info on Global Warming.

Sinuous Jet Stream Brings Winter Months Extremes

The Off-shore United States teleconnection, or PNA, "is really a pattern of climate variability" with good and bad phases, Bowen states.

"In periods of positive PNA, the jet stream is extremely sinuous. Because it is available in from Hawaii and also the Off-shore, it has a tendency to rocket up past Bc towards the Yukon and Alaska, after which it falls lower within the Canadian flatlands and in to the eastern U . s . States. The primary effect when it comes to weather conditions are that people generally have cold winter months throughout the majority of the eastern U.S. You've got a freight vehicle of arctic air that pushes lower there."

Bowen states that whenever the jet stream is curvy, "free airline has a tendency to have mild, relatively warm winters, and Off-shore storms often occur farther north. So in Northern California, the North American and areas of western interior, it is commonly relatively dry, but is commonly quite wet and abnormally warm in northwest Canada and Alaska."

Earlier this winter, there have been occasions of the strongly curving jet stream, and occasions once the Off-shore United States teleconnection was at its negative phase, meaning "the jet stream is flat, mostly west-to-east oriented," and often split, Bowen states. In a long time once the jet stream pattern is much more flat than curvy, "we generally have strong storms in Northern California and Or. That moisture causes it to be in to the western interior. The eastern U.S. isn't impacted by arctic air, therefore it has a tendency to have milder winter temps."

The jet stream pattern -- whether curvy or flat -- has its own finest effects in the winter months and fewer effect on summer time weather, Bowen states. The curvy pattern is enhanced by another climate phenomenon, the El Nino-Southern Oscillation, which transmits a swimming pool of tepid to warm water eastward towards the eastern Off-shore and affects climate worldwide.

Traces of Ancient Rains Reveal Which Way the Wind Blew

Within the millennia, oxygen in ancient rain water was integrated into calcium carbonate deposited in cave and lake sediments. The number of rare, heavy oxygen-18 towards the common isotope oxygen-16 within the calcium carbonate informs geochemists whether clouds that transported the rain were moving generally south or north throughout confirmed time.

Previous research determined the dates and oxygen isotope ratios for sediments within the new study, permitting Bowen and co-workers to make use of the ratios to inform when the jet stream was curvy or flat at various occasions throughout yesteryear 8,000 years.

Bowen states air flowing within the Off-shore accumulates water in the sea. Like a curvy jet stream carries clouds north toward Alaska, the environment cools and a few of the water is lost as rain, with greater proportions of heavier oxygen-18 falling, thus raising the oxygen-18-to-16 ratio in rain and certain sediments in western The United States. Then your jet stream curves south over the center of the region, and also the water vapor, already depleted in oxygen-18, falls within the East as rain with lower oxygen-18-to-16 ratios.

Once the jet stream is flat and moving east-to-west, oxygen-18 in rain continues to be elevated in the western world and depleted within the East, however the difference is a smaller amount than once the jet stream is curvy.

By analyzing oxygen isotope ratios in lake and cave sediments in the western world and East, Bowen and co-workers demonstrated that the flatter jet stream pattern won from 8,000 to 4,000 years back in The United States, however, over only five centuries, the pattern moved to ensure that curvy jet streams grew to become more frequent or severe or both. The technique can't distinguish frequency from severity.

The brand new study relies mainly on isotope ratios at Buckeye Creek Cave, W. Veterans administration. Lake Grinell, N.J. Or Caves National Monument and Lake Jellybean, Yukon.

Additional data supporting growing curviness from the jet stream over recent millennia originated from seven other sites: Crawford Lake, Ontario Castor Lake, Clean. Little Salt Spring, Fla. Estancia Lake, N.M. Crevice Lake, Mont. and Dog and Felker ponds, Bc. Some sites provided oxygen isotope data others demonstrated alterations in weather designs according to tree ring growth or spring deposits.

Replicating the Jet Stream

Like a test of the items the cave and lake sediments revealed, Bowen's team did computer simulations of climate using software that can take isotopes into consideration.

Simulations of climate and oxygen isotope changes in the centre Holocene now resemble, correspondingly, present day flat and curvy jet stream designs, supporting the switch toward growing jet stream sinuosity 4,000 years back.

Why did the popularity start then?

"It had been a when seasonality becomes less strong," Bowen states. The Northern Hemisphere was nearer to the sun's rays throughout the summer time 8,000 years back of computer was 4,000 years back or perhaps is now because of a 20,000-year cycle in Earth's orbit. He envisions a tipping point 4,000 years back when weakening summer time sunlight reduced the equator-to-pole temperature difference and, together with an intensifying El Nino climate pattern, pressed the jet stream toward greater curviness.

View the original article here

Weather pattern could fuel more Ala. tornadoes

HUNTSVILLE, Ala. (AP) – This isn't a tornado warning, nor is the siren about to go screaming across the Tennessee Valley.

Dusty Compton, AP

A tornado roars through Tuscaloosa, Ala., in April 2011.

Dusty Compton, AP

A tornado roars through Tuscaloosa, Ala., in April 2011.

But the potential and the indicators are in place to make the upcoming spring tornado season a rocky one to ride out.

This follows a storm season in 2011 that saw several killer tornadoes lash Alabama.

John Christy, the state climatologist and director of the Earth System Science Center at the University of Alabama in Huntsville, cited the presence of the La Niña weather pattern as a cause for tornado apprehension this spring.

"In a La Niña type year, we tend to have more of these types of experiences with the trailing cold front creating the opportunity for those specific ingredients to provide the high contrast between cold and warm," Christy said.

"We are still in La Niña pattern. The long-range forecast for the spring is for warmer than usual. So that sets up an opportunity for a contrast along the way for these ingredients to come together."

If it happens, Kevin Knupp will be ready. A professor of atmospheric sciences at UAH who studies tornadoes, Knupp is working on research about the influence gravity waves have on tornadoes.

Knupp compared the gravity waves to the way water moves across a lake. As the gravity waves encounter a potential tornado, it can enhance the likelihood of a twister developing, according to Knupp's theory.

"When the waves intersect the storm, oftentimes - not always but most of the time - there is a response from the storm," Knupp said. "If there is an existing circulation, it intensifies that existing circulation there and if there is no tornado genesis, the formation of a tornado can occur at that time."

Watching gravity waves -- which is easier in a humid climate like Alabama -- can aid forecasters in identifying tornadoes. Knupp said the National Weather Service in Huntsville was already using gravity waves among its tools for distinguishing tornadoes.

"We can be more specific on when and where it might form," said Knupp, who is also studying the impact topography has on the intensity of tornadoes. "We want to do that because the false alarm rate on tornado warnings has been so high in this area."

So what's on the horizon for the Tennessee Valley as prime tornado season approaches in March and April?

"From a historical standpoint, Alabama gets about 60 tornadoes a year," Christy said. "Most of them come in the spring. So by any standard measure, you should be ready for something to happen this spring.

"With the way the global atmosphere circulation is set up (with the La Niña pattern), there is a bit more chance that number will be higher than average this spring."

The La Niña pattern, Christy and Knupp said, brings cold air from the Pacific Ocean into close proximity with warm air from the Gulf of Mexico. Christy described it as an "opportunity" for the two air masses to "collide" over Alabama and that's when the atmosphere becomes unstable.

But Christy downplayed any seeming increase in tornadoes in recent years.

"We still have just as many tornadoes as we've ever had," he said. "We just put more stuff in their way to hit. So the damage from tornadoes will just continue to rise."

Of course, weather experts are loathe to look farther into the future than absolutely necessary. But history, in a sense, can be a crystal ball with a peek at what's to come.

"If it happened before, it'll happen again and probably worse," Christy said. "That's my general rule of climate."

Said Knupp, "I remember that word for word and that's what I tell my students."

Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.For more information about reprints & permissions, visit our FAQ's. To report corrections and clarifications, contact Standards Editor Brent Jones. For publication consideration in the newspaper, send comments to letters@usatoday.com. Include name, phone number, city and state for verification. To view our corrections, go to corrections.usatoday.com.

View the original article here

La Nina weather pattern may be factor in more tornadoes (Reuters)

CHICAGO (Reuters) – La Nina, a weather pattern characterized by colder ocean temperatures in the eastern equatorial Pacific, may be playing a part in the high number of U.S. tornadoes this spring, according to an AccuWeather meteorologist.

"La Nina typically has a more active southern jet stream. This spring that has played a role in the severe weather," said Mark Paquette, meteorologist for AccuWeather.com.

Another factor may be warmer temperatures in the Gulf of Mexico, which helped contribute to a warm and muggy air mass in the south, Paquette said.

But meteorologists said it was impossible to determine if climate change is responsible for the surge in natural disasters.

Weather experts agree that the deadly nature of this year's tornadoes is mostly due to bad luck and population sprawl -- as some tornadoes have hit densely populated areas in Missouri and Minnesota over the weekend and Alabama in April.

"We have people where there used to be farmland," said Paquette.

This year has seen an unusually high number of tornadoes, with 1,168 as of May 22, compared to an average of about 671 by this time, according to Joshua Wurman, president of the Center for Severe Weather Research in Boulder, Colo.

This year's tornado season has been exceptionally deadly -- the most recent example being the tornado that hit Joplin, Missouri Sunday, killing at least 116 people.

The U.S. is on pace to break the record for deaths from tornadoes this season, the National Weather Service said on Monday.

CLIMATE CHANGE A FACTOR?

Tornadoes typically form in the spring months as a result of cool air clashing with warm, humid weather. The conditions this spring have been "very favorable" for tornado formation, noted Wurman. He said that these conditions occur in some years with La Nina, but these conditions also can occur without La Nina.

Wurman said scientists are leery of drawing connections between tornadoes and long-term climate change, for a few reasons. One reason is that if something is attributable to a long-term change in climate, it would have to happen repeatedly. Last year was not a high year for tornadoes.

Scientists also do not have a good feel theoretically for what climate change would likely do to the frequency and intensity of tornadoes, Wurman said. While nearly all scientists agree climate change is occurring and globally average temperatures will probably go up, they do not know what that means for tornadoes.

"It could be climate change might cause more tornadoes, or less tornadoes, or there might be no change," Wurman said.

The tornadoes that hit the south in April were exceptional in their number, according to weather experts. What was unusual about Sunday's Missouri tornado was that it made a direct hit on a small city.

"It's bad luck," said Paquette. "Sometimes you have tornadoes that hit in the cornfields of Kansas or Nebraska or Iowa and the only person affected is that farmer and it doesn't even hit his house. But here we have a tornado that hit a hospital."

The expanding population of the United States, with accompanying suburban sprawl, has created more areas for tornadoes to cause serious damage.

Wurman noted that the tornado could have been worse if it hit an even more populated urban area, like the Chicago suburbs. "A tornado doesn't really care what's underneath it," said Wurman.

Wurman said that while it is easier for tornadoes to cause expensive and deadly damage because of sprawl, warnings also are better than they used to be. Thirty years ago, people only got an average of 3 minutes of warning before a tornado hit, now the average is 13 minutes.

"We'd like to get that up to 30 or 40 minutes," Wurman said.

He said he also would like to get the false alarm rate down because 70-75 percent of tornado warnings are false alarms, so people do not always seek shelter in time.

(Writing and reporting by Mary Wisniewski; Editing by Greg McCune)

View the original article here