Columbia Team Shows How Stratospheric Conditions Affect Weather

EARTH OBSERVATION

"The stratosphere has a longer 'memory' than the troposphere," adds co-author Andrew Charlton. "If you want to make forecasts on a time scale longer than several days, it is useful to understand the mechanisms linking places with longer memories, such as the stratosphere and the oceans to the troposphere."

by Jennifer Freeman
Columbia NY (SPX) Dec 09, 2004
Three members of Columbia's Department of Applied Physics and Applied Mathematics have used a simple climate model to demonstrate how the weather systems and storms we experience may be influenced by disturbances in the Earth's stratosphere, the upper layer of atmosphere between 10 and 30 miles high. This Earth Institute research was recently highlighted by the American Geophysical Union, following recent publication in the journal Geophysical Research Letters.

"Our research shows that changes to the strength of winds in the stratosphere cause changes to tropospheric weather systems" explained lead-author Matthew Wittman.

Understanding how the stratosphere affects the troposphere, the lowermost layer of the atmosphere where weather occurs, is important to improving seasonal weather forecasts and predicting the effect of ozone depletion and global warming on our climate.

Each winter a westerly jet - called the Polar Night Jet - forms in the stratosphere. Winds in this jet circulate around the pole at speeds of up to 100 miles per hour. The strength of this jet changes as part of normal atmospheric variability, and possibly also in response to climate change. In their new research, the authors show that the presence of stronger westerly jets in the stratosphere causes tropospheric weather systems to track further towards the pole.

Averaging the changes to the paths of weather systems, the research team showed, produces a pattern of changes similar in structure to the Arctic Oscillation, the dominant pattern of climate variability in the Northern Hemisphere that describes how temperatures across the whole hemisphere vary together.

The research is part of the team's ongoing efforts to understand the interaction of the stratosphere and troposphere and improve the representation of this interaction in climate models. The Columbia co-authors - Matthew Wittman, Lorenzo Polvani, Richard Scott and Andrew Charlton - are affiliated with the climate research group at the Earth Institute at Columbia.

TERRADAILY

Phillipines Storm Leaves 300 Dead, 150 Missing

Real, Philippines (AFP) Nov 30, 2004
Rescuers were desperately searching for survivors Tuesday after floods and landslides unleashed by a tropical storm in the Philippines killed more than 300 people and left at least 150 others missing, many buried alive under tonnes of debris.

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