Abstracts for the 6th International GAME Conf.
3-5 December 2004
Kyoto Japan
Onset of the East Asia Summer Monsoon in 1991 Simulated by an AGCM
K. Ninomiya (1), S. Emori (2), A. Hasegawa (2), T. Nishimura (4), S. Matsumura (4)
(1) Frontier Research Center for Global Change
(2) ibid.
(4) ibid
CCSR/NIES/FRCGC joint modeling group made a 20-year simulation for 1979-1998 by an AGCM (primitive equation spectral model T106L56; the triangular spectral truncation at wave-number 106 with 56 layers) with the observed sea surface temperature. This study presents features of the East Asia summer monsoon simulated for 1991, in comparison with observational studies for this year.
The rain season over the Indochina Peninsula and the South China begins around middle of April, ~ one month prior to the onset of the Indian monsoon. The large precipitation is limited only over the land areas, where the sensible heat flux reaches ~50 W m-2. Owing to this sensible heat flux, the surface temperature rises and the vertical stability decreases over the land areas. In this period, the sensible heat flux over the adjacent sea areas is very small. Consequently, large temperature gradient is sustained between the land and sea areas. The precipitation areas gradually shift northward. A precipitation zone begins to extend from the China toward the Japan Islands. The amount of precipitation due to the grid-scale precipitation is comparable with that due to the cumulus parameterization.
The location of the precipitation areas over the East Asia changes around the end of May, in association with the onset of the Indian monsoon. With the increase of the convergence between the Indian monsoon westerly and the easterly trade wind over the East China Sea, the precipitation area moved once southward over the East China Sea. The precipitation due to cumulus parameterization increases in this period, and nearly moist neutral stratification is maintained. The large heat source presents in the middle-high troposphere. The precipitation zone elongates from the South China Sea toward the Japan Island along the northwestern rim of the North Pacific subtropical anticyclone.
While the Indian monsoon westerly stays almost same latitude during Jun-July, the east Asia rain belt shifts north ward to ~40N in the middle July .
The features of the three stages of the East Asia summer monsoon simulated in the AGCM are consistent with the observed features.
Submittal Information
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Frontier Research Center for Global Change | |
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Show-machi, Kanazawa-ku, Yokohama, 236-0001 | |
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