Climate Dynamics Student Wins Award at Conference

Climate Dynamics Ph.D. student Balachandrudu Narapusetty was awarded
"First Place Poster Presentation" at the AMS 16th Conference on
Air-Sea Interaction in Phoenix, Arizona, in January 2009.  AMS is the
American Meteorological Society, the premier US scientific
organization for atmospheric sciences.

Bala's topic was "Potential contributions of Tropical Instability
Waves in change of eastern equatorial Pacific's climate".  The work is
part of his dissertation and was co-authored by former George Mason
professor Ben Kirtman. 

Bala's work investigates how variations in sea surface temperature (SST) can have surprising effects on rainfall and other atmospheric behavior.  In the equatorial Pacific, large ocean vortices, known as Tropical Instability Waves (TIW's), can make patches of warm and cold water along the equator (top figure).  Bala ran a numerical model of the atmosphere to see the effect of these SST patches. A control experiment simulated the atmosphere under "average" (climatological) ocean conditions, with no TIW's.

In a second experiment, ocean SST included TIW's as a row of warm and cold patches along the equator.  Since at any time there were as many warm patches as cold, the average equatorial Pacific was the same as in the control run.  However, the atmospheric response was not the same (bottom figure), as measured by anomalies (TIW experiment minus control experiment).  Both wind and wind divergence anomalies showed variations over time when averaged over the equatorial region. Negative wind divergence, as shown in the figure, is associated with upward air motion and precipitation.  Thus the presence of relatively small (a few hundred kilometers) SST patterns may produce changes in total rainfall over a much larger region (thousands of kilometers) of ocean.