The Middle And Lower Reaches Of The Yangtze River Rainy Season Event With The Eastern Part Of Northwest Summer Rainfall Contact The Preliminary Study

The NCEP/NCAR global reanalysis data about 55 yean; (1948-2002),the observed data about 2 years(1999-2000),the Meiyu data in the Mid-Lower Reaches of the Yangtze River and the precipitation data at 160 stations in China duing 1951 to 2000 are used in the paper.We present a preliminary study on the relationship between the precipitation total for Meiyu and the summerly precipitation in the eastern side of the northwest China.then using nonhydrostatic version MM5 with one nested grid,the effect of the circulation patterns for Meiyu on the summerly precipitation in the eastern side of the northwest China was simulated by numerical simulation of full physics. We also analyzed the relation between the precipitation for Meiyu and the summerly precipitation in Sichuan ,the areas in southeast China along sea.The main results show as following:1.The correlation between the precipitation total for Meiyu and the summerly precipitation in the east of NW China are negative.In the years of much precipitation total for Meiyu,the center of anticorrelation lies in Tianshui;and in the years of less precipitation total for Meiyu ,the center of nagative correlation extends northwestwards from Tianshui.2.The synthetic flow pattern for the much(less) precipitation total for Meiyu years is same as the typical flow pattern for drought(rainy) years in the east of NW China.3.The correlation between the precipitation total for Meiyu and the summerly precipitation in Sichuan(the areas of southeast China along sea) are negative. In the years of much precipitation total for Meiyu,the center of anticorrelation lies in Chengdu(Fuzhou);and in the years of less precipitation total for Meiyu ,the center of nagative correlation extends southeastwards from Chengdu,and in the areas of southeast China along sea , the center of nagative correlation also lies in Fuzhou. But the correlation between the precipitation total for Meiyu and the summerly precipitation in Xinjiang are not clear.4. In 1999,the dipole existed in between the Okhotsk high and the depression in the north of northeast China, thus the Okhotsk high became active and maintained,the SUBH was located to an area quite further south than usual.The high persisted in the east region of NW China,the cold air flowed to the Mid-Lower Reaches of the Yangtze River along the high.In the eastregion of NW China,air steam under troposphere was strong sinking motion,and formatted the negative vorticity region,the vapour flux divergence was divgence.lt was apparently that the rain couldn't occur in the eastern portin of NW China.In 2000 year,Okhotsk high was very weak or didn't exist in,there was high in the east Asia - Japan,the SUBH is located to an area further north than usual.In the east region of NW China ,the trough maintained,air stream under troposphere was strong ascending motion,the cycolonic circulation was prevailing,the vapour flux divergence was intensive convergences the rain easy happened in the east areas of northwest China.