ANALYSIS OF JULY AND AUGUST PRECIPITATION IN SPATIAL DISTRIBUTION PATTERNS AND ASSOCIATED ATMOSPHERIC CIRCULATION CHARACTERISTICS IN SICHUAN

HUANG Xiao-mei; JIANG Xing-wen; XIAO Ding-mu

doi:10.16032/j.issn.1004-4965.2017.05.009

Abstract：Using the observational monthly precipitation data at 156 stations of Sichuan and ERA-interim monthly reanalysis from 1979 to 2013,we discussed the spatial distribution patterns of precipitation in July and August and the associated large-scale atmospheric circulation characteristics in Sichuan.The results are shown as follows:(1) The principal modes of monthly precipitation anomalies of Sichuan in July and August are consistent distribution,followed by central-east-west oscillation.But the same mode changes in July and August have no continuity;(2) The patterns of circulation which are related to the consistent spatial distribution pattern of different months have significantly different characteristics.With the main atmospheric circulation factors including the Subtropical High (SH) and the circulation in mid-high latitudes of Eurasian continent and the South Asia High (SAH);(3) The intensity and position of key atmospheric circulation factors related to the precipitation anomaly of the consistent spatial distribution pattern in different months have obviously different characteristics.SH is the most eminent one among these factors.The west of SH strengthens and shifts northward and westward slightly in July,while the southwest of SH strengthens and shifts southward and westward obviously in August,inducing the simultaneous monthly rainfall in the whole areas of Sichuan to be more than normal.The northwest of SH strengthens and southwest of SH weakens and shifts eastward and northward obviously in July,while the northwest of SH strengthens and shifts northward and westward obviously in August,leading to the simultaneous monthly rainfall in the whole region of Sichuan to be less than normal.