Surface atmospheric response to Sea Surface Temperature ... - ENS

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Corresponding author address: G. Lapeyre, LMD/IPSL, 24 rue Lhomond, 75005 Paris, France. 7. E-mail: ... Click here to download Manuscript (non-LaTeX).
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Surface atmospheric response to Sea Surface Temperature anomalies under

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different wind conditions

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A. Foussard1,2 , G. Lapeyre1∗ and R. Plougonven1

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1. LMD/IPSL, CNRS, Ecole Polytechnique, Ecole Normale Sup´erieure, Sorbonne Universit´e,

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Paris, France.

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2. Ecole des Ponts ParisTech, Champs-sur-Marne, France.

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∗ Corresponding

author address: G. Lapeyre, LMD/IPSL, 24 rue Lhomond, 75005 Paris, France.

E-mail: glapeyre@lmd.ens.fr Generated using v4.3.2 of the AMS LATEX template

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ABSTRACT 9

The response of the atmospheric boundary layer to mesoscale sea surface

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temperature (SST) is often characterized by a link between wind stress diver-

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gence and downwind SST gradients. In this study, an idealized simulation rep-

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resentative of a storm track above a prescribed stationary SST field is exam-

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ined in order to determine in which background wind conditions that relation

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occurs. The SST field is composed of a mid-latitude large-scale frontal zone

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and mesoscale (40-400km) SST anomalies. Concerning the surface wind, it

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is shown that the divergence of the surface wind can either correlate with the

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Laplacian of the atmospheric boundary layer temperature or with the down-

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wind SST gradient. The first case corresponds to background situations of

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weak winds or of unstable boundary layers at large scales. The response at

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the eddy scale is in agreement with an Ekman balanced adjustment in the

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boundary layer. The second case corresponds to background situations of sta-

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ble boundary layers. The response at the eddy scale is then in agreement with

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strong vertical mixing of momentum. Concerning the divergence of the wind

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stress, it generally resembles downwind SST gradients for stable and unstable

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conditions, in agreement with past studies. However, for weak winds, the di-

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vergence of the wind stress is correlated to some extent with the temperature

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Laplacian. In conclusion, our study reveals the importance of the large-scale

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wind conditions in modulating the surface atmospheric response with differ-

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ent responses in the divergences of surface wind and of wind stress.

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