Interannual and seasonal variation of water circulation over East Asia and the western Pacific
Miki Hattori (1), Kazuhisa Tsuboki (1)
(1) Hydrospheric Atmospheric Research Center, Nagoya University
Interannual and seasonal variations of precipitation in East Asia and the western Pacific from June to August are investigated using global monthly precipitation data, NCEP-NCAR reanalysis and the sea level pressure for 20 years from 1979 to 1998.
According to latitudes of the intense precipitation area and precipitation amounts in June, July and August to the east of the Philippines, three types of seasonal change of precipitation are classified; (A) neither precipitation increase nor northward shift from June to August occurs, (B) precipitation increases gradually and its peak shifts northward from 5N to 15N, and (C) precipitation amount is relatively large in June, decreases in July, and increases suddenly to reach the maximum in August with a northward shift from 15N to 25N.
The seasonal changes of moisture flux and moisture flux convergence at 925 hPa averaged in A, B and C showed that the three types of seasonal changes of precipitation correspond to the amount of moisture flux from the west.
Moreover, seasonal changes of the sea level pressure correspond to the seasonal changes of the moisture fluxes. In June, a positive sea level pressure anomaly is located to the northeast of the Philippines and it is significantly large in A while it is small both in B and C. On the other hand, in August, a negative anomaly is present in the same region and it is large in C and decreases in B and A. In the Indian Ocean, a negative anomaly becomes positive from June to August and increasing rate is large in order of A, B and C. Increase of these anomalies of sea level pressure means strengthening anomalies of anticyclonic circulation in the Indian Ocean and cyclonic circulation to the northeast of the Philippines, that is resulted in intensification of the westerly moisture flow to the Philippines at the lower level.
The northward shift of the large precipitation area to the east of the Philippines corresponds to the sea level pressure to the northeast of the Philippines which indicate a pressure of the western edge of the Pacific high.
The three types of seasonal change of precipitation correspond to seasonal changes of precipitation in China through the northward moisture flux around the Philippines toward China.
Submittal Information
Name :
Date :
Miki Hattori
31-May-01-17:00:33
Organization :
Theme :
Hydrospheric Atmospheric Research Center, Nagoya University
