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  • Lin, Jia-Lin, Klaus M. Weickmann, George N. Kiladis, Brian E. Mapes, Siegfried D. Schubert, Max J. Suarez, Julio T. Bacmeister, and Myong-In Lee, 2008: Subseasonal Variability Associated with Asian Summer Monsoon Simulated by 14 IPCC AR4 Coupled GCMs. Journal of Climate, 21, 4541-4567.

This study evaluates the intraseasonal variability associated with the Asian summer monsoon in 14 coupled general circulation models (GCMs) participating in the Inter-governmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). Eight years of daily precipitation from each modelís 20th century climate simulation are analyzed and compared with daily satellite retrieved precipitation. We focus on the three major components of Asian summer monsoon: the Indian summer monsoon (ISM), the western North Pacific summer monsoon (WNPSM), and the east Asian summer monsoon (EASM), together with the two dominant intraseasonal modes: the eastward and northward propagating boreal summer intraseasonal oscillation (BSIO) and the westward propagating 12-24 day mode.

The results show that current state-of-the-art GCMs display a wide range of skill in simulating the intraseasonal variability associated with Asian summer monsoon. During boreal summer (May-October), most of the models produce reasonable seasonal mean precipitation over the ISM region, but excessive precipitation over WNPSM region and insufficient precipitation over EASM region. In other words, models concentrate their rain too close to the equator in the Western Pacific. Most of the models simulate overly weak total intraseasonal (2-128 day) variance, as well as too little variance for BSIO and the 12-24 day mode. Moreover, models often have difficulty in simulating the eastward propagation of BSIO. Nevertheless, many models simulate well the northward propagation of BSIO, together with the westward propagation of the 12-24 day mode. The northward propagation in these models is thus not simply a NW-SE tilted tail protruding off of an eastward-moving deep-tropical intraseasonal oscillation. Only 4-5 models produce spectral peaks in the BSIO and 12-24 day frequency bands; instead, most of the models display too red a spectrum, i.e. an overly strong persistence of precipitation.

Full Article: http://lightning.sbs.ohio-state.edu/publication.html

Last Updated: 2008-10-23

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