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Interannual rainfall variability over the eastern maritime continent

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Thursday, 27 January 2011
Interannual rainfall variability over the eastern maritime continent
Washington State Convention Center
Hisayuki Kubota, Research Institute for Global Change/ Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan; and R. Shirooka, J. I. Hamada, and F. Syamsudin

The authors investigate the interannual rainfall variability over the eastern maritime continent using station rainfall data in the Republic of Palau and Eastern Indonesia. Two possible mechanisms are proposed to explain the interannual rainfall variability associated with the El Niņo/ Southern Oscaillation over the surrounding region of the Banda and Arafura seas.

During the El Niņo developing year, rainfall starts decreasing close to the equator earlier in summer than off-equatorial region in autumn, such as in mainland Palau. Eastern Indonesia has a dry season during boreal summer in general, and the dry season becomes a significantly drier condition during El Niņo years.

One of the mechanisms for these changes is the air-sea interaction over the Banda and Arafura seas. Intensification of seasonal southerly wind associated with the western North Pacific monsoon decreases sea-surface temperature over the Banda and Arafura seas, and convection is more suppressed during El Niņo years than usual. Another mechanism is the subsidence over the Banda and Arafura seas during the premonsoon of Australian summer monsoon. Land-ocean thermal contrast between Australia and its surrounding seas is intensified during El Niņo years. Shallow thermal convection produces subsidence over the Banda and Arafura seas, and extremely dry condition spreads over the surrounding region of the Banda and Arafura seas in October during El Niņo years.