TY - JOUR T1 - Ocean-Atmosphere Coupling in the Monsoon Intraseasonal Oscillation: A Simple Model Study A1 - Bellon,Gilles A1 - Sobel,Adam H. A1 - Vialard,Jerome AD - Columbia Univ, Dept Appl Phys & Appl Math, New York, NY USA. AD - Columbia Univ, Dept Earth & Environm Sci, New York, NY USA. AD - Univ Paris 06, Inst Rech Dev, Lab Oceanog Expt & Approches Numer, Inst Pierre Simon Laplace, Paris, France. UR - https://archimer.ifremer.fr/doc/00185/29637/ DO - 10.1175/2008JCLI2305.1 KW - madden julian oscillation KW - tropical circulation model KW - sea surface temperature KW - asian summer monsoon KW - convective perturbations KW - walker circulation KW - radiation budget KW - indian ocean KW - variability KW - simulation N2 - 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. Y1 - 2008/10 PB - Amer Meteorological Soc JF - Journal Of Climate SN - 0894-8755 VL - 21 IS - 20 SP - 5254 EP - 5270 ID - 29637 ER -