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University of Tsukuba (1996)

Interannual variation of summer precipitation and water vapor transport over the arid/semi-arid regions in China and Mongolia

Yatagai, Akiyo

Titre : Interannual variation of summer precipitation and water vapor transport over the arid/semi-arid regions in China and Mongolia

Auteur : Yatagai, Akiyo

Grade : Ph. D. in Science 1996

Université de soutenance : University of Tsukuba

Résumé partiel
In this study, interannual variations of sunlnlertinH precipitation over arid and sE’lni ariel regions in China and Iongolia ar investigated. To clarifY the regionality of the inter annual variability of the sunlnler precipitation, an analysi techniqu of rotated e1npiri al orthogonal function (REO F) is applied to a recent 40 year period (1951-1990) of sunlmer pr cipitation. As a result of the REOF 1 five regions have been detennined : I) the Takli nlakan Desert II) the Loess Plateau, III) North China to the central and the southeastern part of Mongolia, IV) the are north of the Tian han Mountains (Junggar Basin), and V) the northern part of Mongolia. To examine how the variations in precipitation for these regions are influenced by th Asian sunlmer monsoon activity in nlid-latitudes correlations with the all-India monthly and seasonal rainfall (IMR) are investigated. The change of atmospheric circulation pat terns related to the interannual variation of regional SU1umer precipitation is also exam ined scrutinized. The results on the regionality and its relation to atmospheric circulation changes are sU1un1arized as follows : 1. Over the Taklimakan Desert, the summer precipitation shows a decadal-scale vari ability, and after 1980 the variability is relatively large. The interannual variation of SU1unler precipitation over the Taklimakan Desert is mainly affected by the upp r trough which appeared around 90 °E in the wet years. The teleconnections far wind ward of n1id-latitude circulations seem to be gr atly responsible for the variation. It is also related to the high pressure system over Central Asia and the eastward (west ward) shift of the Tib tan High in the wet (dry) years. The variation of this region show a clear n gative corr lation with the IMR in J un and July.

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