Analysis Of The Circulation Variations And The Summer Rainfall In Sichuan Province

By using monthly averaged NCEP/NCAR reanalysis data of the atmospheric irculation and the data of summer Precipitation in36meteorological stations in sichuan Province from1979to2010, spatial and temporal characteristics of summer PreciPitation are analyzed,and the relations between the atmospheric circulation and rainfall Patterns are discussed.(1)The basic precipitation Pattern is in phase with each part of the whole province.The summer rainfall is degressive from southeast to northwest of the Province.The difference of rainfall between the south and the north is obvious.and the oscillation Period is abut3-9year.(2)Based on the drought and flood that had been definded, The relation between the atmospheric circulation and rainfall patterns during summer in Sichuan province is discussed. The resultes show that in drought/flood years The West Pacific Subtropical High is stronger and shifts southwestward. The south Asia high is also stronger than normal, and it controls continuously the area over Sichuan. The trough in East Asia. Ural Araea Blocking and Western North Paeific Subtropical High are very important systems influencing the summer Precipiation.Analysis of high-altitude jet stream and the anomaly difference of the flow field, that high-altitude westerly jet in the control of dry cold air and the warm humid water of southern China transport is the main factor affecting the precipitation in the Sichuan region.(3) The south Asia high is stronger and shifts nouthwestward, and The West Pacific Subtropical High is also stronger and shifts nouthwestward, the warm and humid air of the Indian Ocean and South China Sea not conducive to transported to the southwest of china. At the same time, that less cold air activities, northward locations of subtropical high ridgeline, are the main direct causes for the extremely hot and dry weather over the above-mentioned areas in the summer of2006.