Data/hora: 11/06/2024 01:14:18

Provedor de dados: | Institutional Archive of Ifreme (ArchiMer)
País: | France
Título: | Ocean-Atmosphere Coupling in the Monsoon Intraseasonal Oscillation: A Simple Model Study
Autores: | Bellon, Gilles; Sobel, Adam H.; Vialard, Jerome.
Data: | 2008-10
Ano: | 2008
Palavras-chave: | Madden julian oscillation; Tropical circulation model; Sea surface temperature; Asian summer monsoon; Convective perturbations; Walker circulation; Radiation budget; Indian ocean; Variability; Simulation.
Resumo: | A simple coupled model is used in a zonally symmetric aquaplanet configuration to investigate the effect of ocean-atmosphere coupling on the Asian monsoon intraseasonal oscillation. The model consists of a linear atmospheric model of intermediate complexity based on quasi-equilibrium theory coupled to a simple, linear model of the upper ocean. This model has one unstable eigenmode with a period in the 30-60-day range and a structure similar to the observed northward-propagating intraseasonal oscillation in the Bay of Bengal/west Pacific sector. The ocean-atmosphere coupling is shown to have little impact on either the growth rate or latitudinal structure of the atmospheric oscillation, but it reduces the oscillation's period by a quarter. At latitudes corresponding to the north of the Indian Ocean, the sea surface temperature (SST) anomalies lead the precipitation anomalies by a quarter of a period, similarly to what has been observed in the Bay of Bengal. The mixed layer depth is in phase opposition to the SST: a monsoon break corresponds to both a warming and a shoaling of the mixed layer. This behavior results from the similarity between the patterns of the predominant processes: wind-induced surface heat flux and wind stirring. The instability of the seasonal monsoon flow is sensitive to the seasonal mixed layer depth: the oscillation is damped when the oceanic mixed layer is thin (about 10 m deep or thinner), as in previous experiments with several models aimed at addressing the boreal winter Madden-Julian oscillation. This suggests that the weak thermal inertia of land might explain the minima of intraseasonal variance observed over the Asian continent.
Tipo: | Text
Idioma: | Inglês

Identificador:

http://archimer.ifremer.fr/doc/00185/29637/27987.pdf

DOI:10.1175/2008JCLI2305.1

Editor: | Amer Meteorological Soc
Relação: | http://archimer.ifremer.fr/doc/00185/29637/
Formato: | application/pdf
Fonte: | Journal Of Climate (0894-8755) (Amer Meteorological Soc), 2008-10 , Vol. 21 , N. 20 , P. 5254-5270
Fonte: | 2008 American Meteorological Society