Atmosphere Ocean Science Colloquium

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Interaction of Atmospheric and Oceanic Weather

Speaker: Ivy Frenger, Princeton University

Location: Warren Weaver Hall 1302

Date: Wednesday, October 1, 2014, 3:30 p.m.

Synopsis:

The atmosphere is affected by underlying varying sea surface temperatures. Major variability of sea surface temperatures arises from "the oceanic weather", eddies with scales of the order of 100 km which are omnipresent features in the global ocean. First, we analyzed the impact of these transitory and approximately circular sea surface temperature fronts on the overlying atmosphere by examining the atmospheric conditions associated with over 600,000 individual eddies in the Southern Ocean, using satellite data. We show that ocean eddies locally affect near-surface wind, cloud properties and rainfall, i.e. modulating atmospheric weather conditions. The observed pattern of atmospheric change is consistent with a mechanism in which the sea surface temperature anomalies associated with the oceanic eddies modify turbulence in the atmospheric boundary layer. Second, we set-up a regional coupled atmosphere-ocean model for the south Atlantic. The model reproduces the effect which we detected in observations and confirms our hypothesis regarding the dominant mechanism. Examining the feedback of the eddy-caused wind modifications on the ocean, we find it important to resolve lateral wind gradients at the scales of eddies as they result in a significant energy change of the ocean eddies.