The Spatial-temporal Variation Of Persistent Heavy Rainfall In South Of China In Summer And Its Corresponding General Circulation Feature

Based on the data of daily precipitation at 734 stations in China, this paper studies the spatial-temporal features of the persistent heavy rainfall in the south of China in Summer(AMJ) during 1956-2005.By using the method of Empirical Orthogonal Function(EOF), the distribution features of the persistent heavy rainfall in the south of China in Summer is divided into three modes, and the corresponding circulation features to the three modes are also analyzed with compose-analysis. The last part studies some cases to discuss the relationship between the characteristic of Okhotsk Blocking High's movement and the persistent heavy rainfall over the Middle and Lower reaches of the Yangtze River in July. The major conclusions are:(1)The spatial-temporal distribution of the persistent heavy rainfall in the south of China in Summer is uneven. There is an obvious decadal change in the Middle-Lower Reaches of Yangtze River, the times of the persistent heavy rainfall increased obviously in the 1990s; But in the South China region, particularly along the southeast coast of Guangdong, the times of persistent heavy rainfall are relatively stable..(2) The distribution features of the persistent heavy rainfall in the south of China in Summer could be divided into three modes: The first is Consistent-Mode, and it mainly shows that the departure of the persistent heavy rainfall's daily mean precipitation distributes in the east of Guangdong province and the west of Fujian province is identical; The second is Transmeridional-Alternate-Mode, and it mainly shows that the departures in the middle of Guangxi province, in the south-east of Guangdong province and in the east of Jiangxi province are distributed as positive -negative-positive alternating distribution; The third is Latitudinal-Opposition-Mode, and it mainly shows that the distribution of the departure of the persistent heavy rainfall's daily mean precipitation in the Middle and Lower Reaches of Yangtze River and in South China is oppositional.(3) By compose-analysis on the general circulation feature corresponding to the three distribution modes of the persistent heavy rainfall, we got the common features of the corresponding circulation of the three modes: In the typical years when the departure is positive, the abnormal geopotential height at 500hPa from west to east shows a positive-negative-positive alternative distribution in Eurasian continent on the middle-high latitude; In the typical years when the departure is negative, the abnormal geopotential height in the two places where is to the south and to the north of the Baikal Lake shows a negative-positive oppositional distribution.(4) The characteristic of Okhotsk Blocking High's development during the period of Persistent Heavy Rainfall over the Middle-Lower Reaches of Yangtze River in July are divided into two types: Reinforcing-Type and Turning-Type. Furthermore, the Reinforcing-Type can be divided into Immigrating-Mode and Developing-Mode. The former mode is that one blocking high moved eastward into the region of the Okhotsk Sea. The latter mode is that the Okhotsk Blocking High developed by itself in the Okhotsk sea, but no other blocking high moved into this region. The Turning-Type is classified as the Turning-to-Meridional-mode and the Turning-to-Zonal-mode. The former mode is that the direction of the ridge line of Okhotsk Blocking High turned from quasi-zonal direction to quasi-meridional direction. The latter mode is that the direction of the ridge line of Okhotsk Blocking High turned from quasi-meridional direction to quasi-zonal direction.