Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Variable southeast summer rainfall linked to climate change

28.10.2010
A doubling of abnormally wet or dry summer weather in the southeastern United States in recent decades has come from an intensification of the summertime North Atlantic Subtropical High (NASH), or "Bermuda High."

And that intensification appears to be coming from global warming, according to a new analysis by a Duke University-led team of climate scientists.

The NASH is an area of high pressure that forms each summer near Bermuda, where its powerful surface center helps steer Atlantic hurricanes and plays a major role in shaping weather in the eastern United States, Western Europe and northwestern Africa.

By analyzing six decades of U.S. and European weather and climate data, the team found that the center of the NASH intensified by 0.9 geopotential meters a decade on average from 1948 to 2007. (Geopotential meters are used to measure how high above sea level a pressure system extends; the greater the height, the greater the intensity.)

The team's analysis found that as the NASH intensified, its area grew, bringing the high's weather-making western ridge closer to the continental United States by 1.22 longitudinal degrees a decade.

"This is not a natural variation like El Nino," says lead author Wenhong Li, assistant professor of earth and ocean sciences at Duke University's Nicholas School of the Environment. "We thoroughly investigated possible natural causes, including the Atlantic Multivariate Oscillation (AMO) and Pacific Decadal Oscillation (PDO), which may affect highs, but found no links.

"Our analysis strongly suggests that the changes in the NASH are mainly due to anthropogenic warming," she says.

An early online edition of the study, published in the Journal of Climate, is available at the American Meteorological Society's website at http://journals.ametsoc.org/doi/pdf/10.1175/2010JCLI3829.1.

As the NASH intensified and migrated westward, Li's team's analysis found that its north-south movement also was enhanced from 1978 to 2007, a period when the frequency of extreme summer rainfall variability in the Southeast more than doubled over the previous 30 years. From 1978 to 2007, six summers were abnormally wet, while five were abnormally dry. Those 11 summers – defined in this study as the months of June, July and August – had total seasonal precipitation anomalies greater than one standard deviation from the mean.

To forecast future trends in the NASH's intensity, the team used climate models developed for use by the Intergovernmental Panel on Climate Change's Fourth Assessment Report in 2007. The models – known as Coupled Model Intercomparison Project Phase 3 (CMIP3) models – predict the NASH will continue to intensify and expand as concentrations of carbon dioxide and other greenhouse gases increase in Earth's atmosphere in coming decades.

"This intensification will further increase the likelihood of extreme summer precipitation variability – periods of drought or deluge – in southeastern states in coming decades," Li says.

If the NASH 's western ridge jogs a little to the north as it expands, the likelihood increases for more extreme dry weather in the Southeast that summer, she explains. If the NASH wobbles a little to the south, extreme wet weather becomes more likely.

Li's coauthors are Laifong Li of Duke University; Rong Fu of the University of Texas at Austin; Yi Deng of the Georgia Institute of Technology; and Hui Wang of the National Atmospheric and Oceanic Administration's Climate Prediction Center in Camp Spring, Md., and Wyle Information Systems in McLean, Va.

In addition to long-term rainfall data and the CMIP3 models, the team conducted the study on atmospheric reanalysis data from the U.S. National Center for Environmental Prediction/National Center for Atmospheric Research and the European Centre for Medium-Range Weather Forecasts.

Funding for the study came from Duke University and the Nicholas School Office of the Dean.

Tim Lucas | EurekAlert!
Further information:
http://www.duke.edu

More articles from Earth Sciences:

nachricht Ice cave in Transylvania yields window into region's past
28.04.2017 | National Science Foundation

nachricht Citizen science campaign to aid disaster response
28.04.2017 | International Institute for Applied Systems Analysis (IIASA)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>