Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

North Atlantic Oscillation part of the global picture

10.12.2002


An especially cold winter in Europe, lots of snow in Scandinavia or lots of rain in the Mediterranean are all symptoms of what meteorologists call the North Atlantic Oscillation, but a group of Penn State researchers has gone beyond the symptoms to try to decipher the dynamics of this atmospheric pattern.



"Some scientists argue that the impact of the NAO on global climate is comparable to El Nino," says Dr. Sukyoung Lee, associate professor of meteorology. "However, most of the scientific community’s analyses to date have been of monthly or seasonal averages which fail to reveal the intrinsic nature of the NAO." The fundamental dynamic process of the North Atlantic Oscillation is on a two-week scale, says Dr. Christian Franzke, postdoctoral fellow in meteorology, referencing an earlier work by Dr. Steven Feldstein, senior research associate, Penn State’s Environmental Institute. Looking at seasonal data does not really say anything about the causes or mechanisms of the phenomenon. Franzke presents this research at the fall meeting of the American Geophysical Union today (Dec. 9).

The NAO is best known as a pressure difference between the air over Iceland and the air over the Azores – located in the middle of the Atlantic on a latitude with Lisbon, Portugal. If pressure is higher than usual over Iceland, it is colder in Europe during the winter and there is more rain in the Mediterranean. If pressure is anomalously low over Iceland, there are more storms and precipitation in Europe, a milder winter and there is less rain in the Mediterranean.


"The NAO has a strong influence on European weather and is an economic issue as well for fish production and agriculture," says Franzke.

The NAO occurs in the tropopause, the areas of the atmosphere between the troposphere and the stratosphere at between 7 to 10 miles above the Earth’s surface. A stream of air called the Polar Front Jet Stream moves from the Pacific, across North America and over the Atlantic Ocean.

During the typical winter season, there are about two or three separate NAO incidents, some positive and some negative.

Franzke, Lee and Feldstein looked at 40 years of daily weather data gathered by the National Center for Atmospheric Research. This data includes measures of temperature, pressure, wind speed and direction, and surface pressure. They used existing climate models to recreate the patterns associated with the NAO and compared those to observational data.

In the Atlantic, they found that the stream sometimes moves in a breaking wave pattern and is oriented either from the northwest to the southeast or from the southwest to the northeast. Each breaking wave takes about six days to form and then disappear and is usually followed by a second wave, completing the two-week pattern. The wave crest can actually collapse and become flat just as ocean waves do, initiating a period of no NAO. When the wave breaks with an orientation from the southwest to northeast, the pattern is considered positive and produces low pressure over Iceland making European winters warmer. When the wave breaks in the opposite direction – southeast to northwest – higher than usual pressure forms over Iceland and European winter is cold. This is a negative incident.

"The recent trend toward global warming shows more bias toward positive phase NAOs," says Franzke. "There are more positive than negative events occurring during a winter."

This would tip the winter weather pattern toward one of milder winters in Europe.

The researchers also found that episodes of NAO are linked to storms in the Pacific Ocean. A storm in the Pacific will create one breaking wave pattern. If the storm is in the northern Pacific, than there will likely be a negative NAO. If the storm starts farther south, the NAO probably will be positive. If a series of storms follows each other, then an NAO episode will last longer. If there are no storms entering the North Atlantic, the NAO dies out.

"Because of this connection to Pacific storms, it might be possible to predict the changes in European weather four or five days in advance," says Franzke.

With so much interest in global warming, we definitely need to understand the mechanism of NAO before we begin to make any predictions, says Feldstein.

The researchers have not yet looked at the effects of the NAO on North American weather, but Franzke states that there is an influence on Eastern Seaboard weather. With Pacific storms implicated in NAO formation, and the Pacific the controlling factor for El Nino, there might be a strong link between the two phenomena. However, to fully understand the global links, the North Atlantic Oscillation must be fully understood.

Andrea Elyse Messer | EurekAlert!
Further information:
http://www.psu.edu/

More articles from Earth Sciences:

nachricht From volcano's slope, NASA instrument looks sky high and to the future
27.04.2017 | NASA/Goddard Space Flight Center

nachricht Penn researchers quantify the changes that lightning inspires in rock
27.04.2017 | University of Pennsylvania

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

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

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Bare bones: Making bones transparent

27.04.2017 | Life Sciences

Study offers new theoretical approach to describing non-equilibrium phase transitions

27.04.2017 | Physics and Astronomy

From volcano's slope, NASA instrument looks sky high and to the future

27.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>