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 Hundreds of bubble streams link biology, seismology off Washington's coast
22.03.2019 | University of Washington

nachricht Atmospheric scientists reveal the effect of sea-ice loss on Arctic warming
11.03.2019 | Institute of Atmospheric Physics, Chinese Academy of Sciences

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: The taming of the light screw

DESY and MPSD scientists create high-order harmonics from solids with controlled polarization states, taking advantage of both crystal symmetry and attosecond electronic dynamics. The newly demonstrated technique might find intriguing applications in petahertz electronics and for spectroscopic studies of novel quantum materials.

The nonlinear process of high-order harmonic generation (HHG) in gases is one of the cornerstones of attosecond science (an attosecond is a billionth of a...

Im Focus: Magnetic micro-boats

Nano- and microtechnology are promising candidates not only for medical applications such as drug delivery but also for the creation of little robots or flexible integrated sensors. Scientists from the Max Planck Institute for Polymer Research (MPI-P) have created magnetic microparticles, with a newly developed method, that could pave the way for building micro-motors or guiding drugs in the human body to a target, like a tumor. The preparation of such structures as well as their remote-control can be regulated using magnetic fields and therefore can find application in an array of domains.

The magnetic properties of a material control how this material responds to the presence of a magnetic field. Iron oxide is the main component of rust but also...

Im Focus: Self-healing coating made of corn starch makes small scratches disappear through heat

Due to the special arrangement of its molecules, a new coating made of corn starch is able to repair small scratches by itself through heat: The cross-linking via ring-shaped molecules makes the material mobile, so that it compensates for the scratches and these disappear again.

Superficial micro-scratches on the car body or on other high-gloss surfaces are harmless, but annoying. Especially in the luxury segment such surfaces are...

Im Focus: Stellar cartography

The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.

A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...

Im Focus: Heading towards a tsunami of light

Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.

"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

International Modelica Conference with 330 visitors from 21 countries at OTH Regensburg

11.03.2019 | Event News

Selection Completed: 580 Young Scientists from 88 Countries at the Lindau Nobel Laureate Meeting

01.03.2019 | Event News

LightMAT 2019 – 3rd International Conference on Light Materials – Science and Technology

28.02.2019 | Event News

 
Latest News

Solving the efficiency of Gram-negative bacteria

22.03.2019 | Life Sciences

Bacteria bide their time when antibiotics attack

22.03.2019 | Life Sciences

Open source software helps researchers extract key insights from huge sensor datasets

22.03.2019 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>