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Article Dans Une Revue Climate Dynamics Année : 2013

Impact of projected SST changes on summer rainfall in southeastern South America

Résumé

Recent studies have shown that global warming and associated sea-surface temperature (SST) changes may trigger an important rainfall increase in southeastern South America (SESA) during the austral summer (December-January-February, DJF). The goal of this paper is to provide some insight into processes which may link global and SESA changes. For this purpose, a "two-way nesting" system coupling interactively the regional and global versions of the LMDZ4 atmospheric model is used to study the response to prescribed SST changes. The regional model is a variable-grid version of the global model, with a zoom focused over South America. An ensemble of simulations forced by distinct patterns of DJF SST changes has been carried out using a decomposition of full SST changes into their longitudinal and latitudinal components. The full SST changes are based on projections for the end of the twenty-first century from a multi-model ensemble of WCRP/CMIP3. Results confirm the presence of a major rainfall dipole structure, characterized by an increase in SESA and a decrease in the South Atlantic Convergence Zone region. Rainfall changes found in the WCRP/CMIP3 models are largely explained as a response of this dipole structure to the zonally-asymmetric (or longitudinal) component of SST changes. The rainfall response to the zonal-mean (or latitudinal) SST changes (including the global warming signal itself) shows an opposite contribution. The processes explaining the role of zonally-asymmetric SST changes involve remote effects of SST warming over the equatorial Indian and Pacific oceans inducing an atmospheric wave-train extended across the South Pacific into South America. © 2013 Springer-Verlag Berlin Heidelberg.

Domaines

Climatologie

Dates et versions

hal-01096294 , version 1 (17-12-2014)

Identifiants

Citer

C. Junquas, C.S. Vera, L. Li, Hervé Le Treut. Impact of projected SST changes on summer rainfall in southeastern South America. Climate Dynamics, 2013, 40 (7-8), pp.1569-1589. ⟨10.1007/s00382-013-1695-y⟩. ⟨hal-01096294⟩
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