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Mesoscale SST–wind stress coupling in the Peru–Chile current system: Which mechanisms drive its seasonal variability?

Mesoscale SST–wind stress coupling in the Peru–Chile current system: Which mechanisms drive its seasonal variability?
Mesoscale SST–wind stress coupling in the Peru–Chile current system: Which mechanisms drive its seasonal variability?
Satellite observations and a high-resolution regional ocean–atmosphere coupled model are used to study the air/sea interactions at the oceanic mesoscale in the Peru–Chile upwelling current system. Coupling between mesoscale sea surface temperature (SST) and wind stress (WS) intensity is evidenced and characterized by correlations and regression coefficients. Both the model and the observations display similar spatial and seasonal variability of the coupling characteristics that are stronger off Peru than off Northern Chile, in relation with stronger wind mean speed and steadiness. The coupling is also more intense during winter than during summer in both regions. It is shown that WS intensity anomalies due to SST anomalies are mainly forced by mixing coefficient anomalies and partially compensated by wind shear anomalies. A momentum balance analysis shows that wind speed anomalies are created by stress shear anomalies. Near-surface pressure gradient anomalies have a negligible contribution because of the back-pressure effect related to the air temperature inversion. As mixing coefficients are mainly unchanged between summer and winter, the stronger coupling in winter is due to the enhanced large-scale wind shear that enables a more efficient action of the turbulent stress perturbations. This mechanism is robust as it does not depend on the choice of planetary boundary layer parameterization.
Ocean–atmosphere interactions, Mesoscale SST–wind stress coupling, Regional coupled modeling, Eastern Boundary Upwelling System
0930-7575
2309-2330
Oerder, Vera
7be15d2a-4244-4be4-96fa-75b038d45325
Colas, François
9273d715-a42a-41c5-86e6-d86a33fb982e
Echevin, Vincent
0084bacf-4548-40d0-9e44-f8767c19b178
Masson, Sebastien
2347d09d-6ab2-4b91-992a-7d73e67b7879
Hourdin, Christophe
972144b2-417b-4243-a484-87bfa4b4815e
Jullien, Swen
7df84684-a8bc-4d92-929a-b4664238fa67
Madec, Gurvan
ffb28deb-4bbd-4a4c-914f-492f813e4864
Lemarié, Florian
070de88d-bb63-4a61-8d93-22c4121f9c52
Oerder, Vera
7be15d2a-4244-4be4-96fa-75b038d45325
Colas, François
9273d715-a42a-41c5-86e6-d86a33fb982e
Echevin, Vincent
0084bacf-4548-40d0-9e44-f8767c19b178
Masson, Sebastien
2347d09d-6ab2-4b91-992a-7d73e67b7879
Hourdin, Christophe
972144b2-417b-4243-a484-87bfa4b4815e
Jullien, Swen
7df84684-a8bc-4d92-929a-b4664238fa67
Madec, Gurvan
ffb28deb-4bbd-4a4c-914f-492f813e4864
Lemarié, Florian
070de88d-bb63-4a61-8d93-22c4121f9c52

Oerder, Vera, Colas, François, Echevin, Vincent, Masson, Sebastien, Hourdin, Christophe, Jullien, Swen, Madec, Gurvan and Lemarié, Florian (2016) Mesoscale SST–wind stress coupling in the Peru–Chile current system: Which mechanisms drive its seasonal variability? Climate Dynamics, 47 (7-8), 2309-2330. (doi:10.1007/s00382-015-2965-7).

Record type: Article

Abstract

Satellite observations and a high-resolution regional ocean–atmosphere coupled model are used to study the air/sea interactions at the oceanic mesoscale in the Peru–Chile upwelling current system. Coupling between mesoscale sea surface temperature (SST) and wind stress (WS) intensity is evidenced and characterized by correlations and regression coefficients. Both the model and the observations display similar spatial and seasonal variability of the coupling characteristics that are stronger off Peru than off Northern Chile, in relation with stronger wind mean speed and steadiness. The coupling is also more intense during winter than during summer in both regions. It is shown that WS intensity anomalies due to SST anomalies are mainly forced by mixing coefficient anomalies and partially compensated by wind shear anomalies. A momentum balance analysis shows that wind speed anomalies are created by stress shear anomalies. Near-surface pressure gradient anomalies have a negligible contribution because of the back-pressure effect related to the air temperature inversion. As mixing coefficients are mainly unchanged between summer and winter, the stronger coupling in winter is due to the enhanced large-scale wind shear that enables a more efficient action of the turbulent stress perturbations. This mechanism is robust as it does not depend on the choice of planetary boundary layer parameterization.

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More information

Accepted/In Press date: 21 December 2015
e-pub ahead of print date: 8 January 2016
Published date: October 2016
Keywords: Ocean–atmosphere interactions, Mesoscale SST–wind stress coupling, Regional coupled modeling, Eastern Boundary Upwelling System
Organisations: Marine Systems Modelling

Identifiers

Local EPrints ID: 402325
URI: http://eprints.soton.ac.uk/id/eprint/402325
ISSN: 0930-7575
PURE UUID: 8e0bdb33-0876-4c74-9cbe-eef6f8642b1a

Catalogue record

Date deposited: 03 Nov 2016 14:34
Last modified: 15 Mar 2024 03:13

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Contributors

Author: Vera Oerder
Author: François Colas
Author: Vincent Echevin
Author: Sebastien Masson
Author: Christophe Hourdin
Author: Swen Jullien
Author: Gurvan Madec
Author: Florian Lemarié

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