Temporal and spatial distribution and circulation features of the Meiyu precipitation anomaly in Jiangsu in the latest 50 years

Based on daily precipitation data from 66 stations in Jiangshu province from 1961 to 2009 and the NCEP/NCAR reanalysis data,Empirical Orthogonal Function (EOF), Morlet wavelet analysis and composite analysis methods were used to investigate temporal and spatial change and circulation features of the Meiyu precipitation anomaly in Jiangsu in the latest 50 years. The results show that the Meiyu precipitation in Jiangsu presented 3 main spatial patterns, i.e., the consistent pattern in the whole region, the spatial reverse pattern between the north and south (bordered by 32°N) and the spatial reverse pattern among the Yangtze-Huaihe River region and other regions in Jiangsu. Anomalous Meiyu precipitation in Jiangsu has the significant inter-annual and decadal change, presenting quasi-two-year, quasi-four-year and quasi-six-year periodic oscillation. Meiyu precipitation in Jiangsu in the latest 50 years presents a trend of increase and presents obviouslypositive trend in Huaibei and the southern part of Jiangshu province with over 95% confidence level. In addition, South Asia high has an eastward central zone, weaker intensity and smaller area; but subtropical high moves westward and the ridge point is easterly, 588-dagpm isoline is northward and area is bigger; the dry and cold air led by the Northeast China cold vortex moves southward and interacts with strong southwest warm and wet airflow in Jiangsu resulting in precipitation more than that in the same period of normal years in all High Meiyu years. The circulation patterns in all Low Meiyu years are contrary to the patterns mentioned above.