Bellon G. auteur aut IRD Sobel A. H. auteur aut IRD Vialard Jérôme auteur aut IRD text journalArticle eng text/pdf born digital access 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. specialized 021 032 21 20 5254-5270 2008 0894-8755 https://www.documentation.ird.fr/hor/fdi:010044088 10.1175/2008jcli2305.1 0894-8755 [F B010044088] https://www.documentation.ird.fr/hor/fdi:010044088 https://www.documentation.ird.fr/intranet/publi/2008/11/010044088.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2008-12-05 2017-08-23 fdi:010044088 fre