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A Peculiar Feature of the Seasonal Migration of the South American Rain Band

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タイトル: A Peculiar Feature of the Seasonal Migration of the South American Rain Band
著者: Tanimoto, Youichi 著作を一覧する
Kajitani, Takushi 著作を一覧する
Okajima, Hideki 著作を一覧する
Xie, Shang-Ping 著作を一覧する
発行日: 2010年 3月19日
出版者: Meteorological Society of Japan
誌名: Journal of the Meteorological Society of Japan
巻: 88
号: 1
開始ページ: 79
終了ページ: 90
出版社 DOI: 10.2151/jmsj.2010-106
抄録: Seasonal migration of tropical rainfall is examined in the South American sector and compared with that over Africa, using satellite and reanalysis data. While the African rain band moves continuously back and forth across the equator following the seasonal march of the sun, the South American one displays a peculiar asymmetry between its northward and southward migration. The rain band moves gradually northward from October to July from the Amazon toward the Caribbean Sea, while its return to the Amazon is an abrupt event, with convection developing rapidly in October around 10°S without going through the equator. Over the equatorial Amazon during July-October, equivalent potential temperature (θe) is kept low by the easterly advection of low temperature and humidity air from the equatorial Atlantic, coinciding with the seasonal development of ocean upwelling and a cold tongue in sea surface temperature. The low θe values prevent convection from developing in the equatorial Amazon while warm SST supports convection on the north coast of South America during August-October. Meanwhile solar radiation continues to heat up the land surface to the south, eventually triggering the onset of deep convection there in October. Atmospheric general circulation model experiments were conducted to examine the effect of the Atlantic cold tongue on tropical rain bands. Without the seasonal development of the Atlantic cold tongue, surface θe remains high in September, and rainfall in the equatorial Amazon switches to a pronounced semi-annual cycle with a peak in each equinox. These results illustrate the role of the Atlantic cold tongue in the peculiar meridional migration of the observed South American rain band.
資料タイプ: article
出現コレクション:雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

提供者: 谷本 陽一


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