7B.5
Tropical intraseasonal oscillations simulated in the U. Hawaii CGCM
Xiouhua Fu, IPRC, University of Hawaii, Honolulu, HI
ABSTRACT
A fully coupled GCM without heat flux correction is developed at U. Hawaii. The hybrid CGCM is composed of an ECHAM T30 AGCM and UH intermediate ocean model (only in the tropical Indian and Pacific Oceans). The model simulations of the tropical Asia-Pacific climate and variability are among the best in comparison to other state-of-the-art CGCMs around the world. However, it also suffers same biases commonly existed in many other CGCMs, such as the warm bias in the southeast Pacific, which is primarily due to the lack of enough stratocumulus in the atmospheric boundary layer. Otherwise, this hybrid CGCM produces fairly realistic annual cycle, monsoons, ENSO and intraseasonal oscillations.
The simulated tropical intraseasonal oscillations (TISO) exhibit significant seasonality as in the observations. In boreal winter (NDJFMA), the TISO action centers are primarily located in the southeast Indian Ocean and Pacific SPCZ region. The dominant ISO mode is the eastward-propagating MJO. In boreal summer (MJJASO), major TISO activities shift to the Northern Hemisphere, with dominant northeast-propagating mode in the Indian and western Pacific regions.
The relationships between the TISO intensity and some mean states (e.g. SST, rainfall, 850mb zonal winds, zonal wind shear between 850mb and 200mb, divergences at 850mb and 950mb) are examined. Though the TISO activities show some connections with all the above mean states, the best pattern match occurs with mean rainfall. The possible implications of these relationships are discussed.
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Session 7B, intraseasonal variability I
Tuesday, 4 May 2004, 1:30 PM-3:15 PM, Napoleon I Room
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