著者

Wataru MORISHIMA Takehiko MIKAMI

出版者

The Association of Japanese Geographers

雑誌

Geographical review of Japan, Series B (ISSN:02896001)

巻号頁・発行日

vol.71, no.2, pp.85-99, 1998-12-01 (Released:2008-12-25)

参考文献数

30

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Interannual variations of summer rainfall over Asia and their associations with geopotential heights in the Northern Hemisphere, tropical convective activities and global sea surface temperature (SST) anomalies are investigated. The Empirical Orthogonal Function (EOF) analysis is applied to the summer rainfall data (JJAS) at 220 stations from 1951 to 1991 in order to reveal the spatial structure and its temporal evolution in the interannual variation of summer rainfall over the Asian region including from India to East Asia. The EOF 1 is detected as the component associated with the Warm Event of ENSO. In other words, the spatial pattern and its time coefficients of EOF 1 indicate that the amount of precipitation decreases over India and the north of China in El Nina years. The EOF 2 has a spatial structure with the same sign from India to East Asia; in particular accompanied with large signals in the middle latitude of East Asia. The variations of these EOFs are connected with those of tropical convective activities and SST anomalies. The variation of EOF 1 is suggested to be associated with the movement of heat source from southeastern Tibet to the southwestern part of China from the correlation coefficients pattern both for the geopotential height fields and the OLR. On the other hand, the EOF 2 is related to variations of convective activities extending from the north of the Philippines to the eastward along 15°N, which are accompanied by negative correlation coefficients to the variation of SST anomalies from the South China Sea to the eastern equatorial Indian Ocean.

著者

Zhenhao BAO Takehiko MIKAMI

出版者

The Association of Japanese Geographers

雑誌

Geographical review of Japan, Series B (ISSN:02896001)

巻号頁・発行日

vol.71, no.1, pp.59-71, 1998-06-30 (Released:2008-12-25)

参考文献数

43

被引用文献数

1 1

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High negative correlation between summer rainfall anomaly in the Yangtze Valley and the middle reaches of the Yellow River in China is shown. Rainfall Anomaly Index (RAI) and the Student's t-test revealed a decadal fluctuation of RAI in the Yangtze Valley at the end of the 1970s. The results concerning correlation between RAI and atmospheric circulation indices show that the variation of summer RAI in the Yangtze Valley is closely related to western Pacific subtropical high index (20-30°N, 130-170°E) at 500 hPa-level in May and westerly zonal index (40-60°N, 90-170°E) at 500 hPa-level in July. The decadal fluctuation of RAI at the end of the 1970s in the Yangtze Valley corresponds to the fluctuation of westerly zonal index in July and western Pacific subtropical high index in May. The impact of sea surface temperature (SST) (EQ-14°N, 130-150°E) in the western Pacific Ocean on RAI in the Yangtze Valley is also discussed. The negative correlation between the SST in June and summer RAI in the Yangtze River at the end of 1970s exhibits a clear atmospheric-oceanic teleconnection. It is closely associated with rainy conditions in the Yangtze Valley during El Niño in the period 1978-1991.