Climate Characteristics Of Continuous Autumn Rain In China And Its Relation With Atmospheric Circulation

Based on the daily meteorological data of753observational stations in China and daily NCEP/NCAR reanalysis data from1961to2010, the meteorological characteristics of continuous autumn (SON) rain and continuous autumn rain of different levels (5-7d,8-10d,11d and above) in China are analyzed. Divided into four regions, namely North China, Southwest China, Changjiang-Huaihe basin and South China. And the main circulation in four regions of continuous autumn rain and continuous autumn rain of different levels are also analyzed. Results show:(1)Distribution characteristics of50a cumulative frequency, annual precipitation and50a cumulative days of continous autumn rain are similar with each other, and also their standard deviation distribution characteristics. The frequency of continuous autumn rain mainly concentrates in the upper reaches of the Yangtze River. The high value zone of the frequency of continuous autumn rain of different levels distributes with the increasing levels, from the southeast to the southwest region. Continuous rain duration is different in different regions. There are mainly11d and above in Southwest. Other regions are5-7d. Continuous autumn rain and continuous autumn rain of different levels occur in Septempter in most parts of China.(2)During continuous autumn rain in the North China, there are negative anomalies and the west and the east is positive anomalies. At500hPa, the main circulation system is the Ural ridge and East Asian trough, the high ridge of8-10d are the strongest. During continuous autumn rain in the South China, there are positive and negative anomalies, At500hPa, the main circulation system is northern India trough and subtropical high pressure, the trough of11d and above is strongest, then8-10d,5-7d is the weakest. The location of subtropical high pressure of8-10d is trending to the west, then11d and above. During continuous autumn rain in the Changjiang-Huaihe basin, there are positive and negative anomalies, At500hPa, circulation systems is significantly different in high-latitude, the main circulation system is Lake Balkhash trough, East Asian trough and subtropical high pressure. The Lake Balkhash trough of11d and above is strongest, then5-7d,8-10d is the weakest.the location of East Asian trough is trending to east.the subtropical high pressure of5-7d is strongest,then8-10d. During continuous autumn rain in the South China, there are negative anomalies,the south is positive. At500hPa, the westerly circulation relatively is flat of5-7d, there are two troughs and a ridge of8-10d and two ridges and two troughs of11d and above.(3)In different areas, during continuous autumn rain and continuous autumn rain of different levels, the circulation system of700hPa height field is weaker than500hPa. At850 hPa wind field, each area is the gathering place by abnormal southerly and northerly wind or controlled by abnormal southerly wind, and also the junction palce by southerly winds and northerly winds or controlled by southerly winds. In different areas, during continuous autumn rain of different levels, the circulation patterm of the case coincides with the average state.