ESC seminar No. 62
The response of the atmospheric Ekman layer and Ekman pumping to sea surface temperature fronts
- Date
- Thursday, November 24, 2011, 10:30-11:30
- Place
- Meeting room 1&2 , 2F Conference Building, YES
- Speaker
- Dr. Niklas Schneider
( IPRC, University of Hawaii ) - Language
- English
Abstract
The impacts of sea surface temperature (SST) fronts on the atmospheric Ekman layer and Ekman pumping are studied in the Gulf Stream region.
Using the high-resolution operational ECMWF analysis, we characterize SST fronts by their impact on the air-sea temperature difference, and show that ocean fronts nonlinearly couple near--surface momentum, thermal and vorticity boundary layers. In response to tropospheric pressure gradients, winds passing over SST fronts lead to downstream air-sea heat fluxes that affect the boundary--layer stability and near--surface pressure gradients. On subinertial time scales, the surface wind stress results from the sea--level pressure gradient, surface thermal wind and stability--dependent vertical mixing. The Ekman pumping induced secondary circulation adjusts the near--surface virtual temperature gradient and so reduces the wind--stress curl to a small residual within a spin--down time-scale as short as several inertial periods for SST fronts. The spin-down due to Ekman pumping couples frontal impacts on boundary--layer stability and pressure gradients.
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