Comparative studies on the seasonal evolution of Asian and North American monsoons -scope for the CEOP-
Jun Matumoto (1)
(1) University of Tokyo
Although sometimes referred to as gNorth American monsoonh, the seasonal evolution of Asian and North American monsoons is found to be very much different. In Asian summer monsoon system (SEAM), low-level pressure lowers due to strong heating over the continent in early summer. It induces low-level monsoon westerlies at the monsoon onset phase, accompanied with the northward shift of the ITCZ. Similar situations occur during the onset phase of the western North Pacific monsoon (WNPM), although the timing is about one to two months later than in SEAM. On the other hand, in the North American continent, large-scale low-level pressure becomes higher, although near surface atmosphere is warming during early summer transition. This is probably due to the dynamical effect of the northwestward extension of the North Atlantic High, and is not directly related with the northward shift of ITCZ. Therefore, no large-scale invasion of monsoon westerlies occurs over the North American Continent, although summer-time precipitation occurs in the southwestern US and west coast of Mexico. On the other hand, ITCZ over the eastern North Pacific intensifies during mid-summer making this oceanic monsoon (ENPM) being more pronounced than over the North American Continent. It is not yet clear if the existence of the North American Continent has some relationship with the development of ENPM. Further comparative studies on the seasonal change processes as well as water and energy cycles among major monsoon systems should be conducted, and why such differences are generated through atmospheric-ocean-land surface coupling processes should be solved through the CEOP studies.
Submittal Information
Name :
Date :
Jun Matsumoto
29-May-01-16:58:48
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Department of Earth and Planetary Science, University of Tokyo
