Indirect air–sea interactions simulated with a cou

Authors: Igor Esau

Publish Date: 2014/04/09

Volume: 64, Issue: 5, Pages: 689-705

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Abstract

A turbulenceresolving parallelized atmospheric largeeddy simulation model PALM has been applied to study turbulent interactions between the humid atmospheric boundary layer ABL and the salt water oceanic mixed layer OML The most energetic threedimensional turbulent eddies in the ABL–OML system convective cells were explicitly resolved in these simulations This study considers a case of shearfree convection in the coupled ABL–OML system The ABL–OML coupling scheme used the turbulent fluxes at the bottom of the ABL as upper boundary conditions for the OML and the sea surface temperature at the top of the OML as lower boundary conditions for the ABL The analysis of the numerical experiment confirms that the ABL–OML interactions involve both the traditional direct coupling mechanism and much less studied indirect coupling mechanism Garrett Dyn Atmos Ocean 2319–34 1996 The direct coupling refers to a common fluxgradient representation of the air–sea exchange which is controlled by the temperature difference across the air–water interface The indirect coupling refers to thermal instability of the Rayleigh–Benard convection which is controlled by the temperature difference across the entire mixed layer through formation of the large convective eddies or cells The indirect coupling mechanism in these simulations explained up to 45  of the ABL–OML covariability on the turbulent scales Despite relatively small amplitude of the sea surface temperature fluctuations persistence of the OML cells organizes the ABL convective cells Water downdrafts in the OML cells tend to be collocated with air updrafts in the ABL cells The study concludes that the convective structures in the ABL and the OML are coorganized The OML convection controls the air–sea turbulent exchange in the quasiequilibrium convective ABL–OML system

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