Analysis Of Precipitation Anomalis Of The Middle And Lower Reaches Of The Yangtze River In June-july2010

Based on the daily precipitation dataset of740stations in China from1951to2010, NCEP/NCAR reanalysis data from1979to2010, and the monthly mean sea surface temperatures and mothly mean sea surface temperatures anomaly (SSTA) provided by the U. S. Climate Prediction Center (CPC). We examined the Precipitation Anomalies during June-July2010in the Middle and lower reaches of the Yangtze River (MLYR). Then, based on the diagnostic results, we simulated the precipitation in this place using NCAR CAM3atmospheric general circulation model (AGCM). The mainly results are as follows:(1) Strong El Nino events had occurred during2009-2010. Under the large-scale climate background, we divided the Meiyu period into three phases. Rain bands concentrated in the MLYR in7-11June. And then, the center moved to Southern China in18-22June, there still had precipitation peak in the MLYR. At last, rain band center back to the MLYR in7-17July.(2) The strong cold air down to south was the main reason why the rain band was more southward in the second stage. The warm shear line and weak warm shear line appeared in the first stage and the third stage in the MLYR mainly caused these two precipitations.(3) The west ridge point index of the Subtropical Western Pacific high and the MLYR precipitation in June-July2010. had a significant negative correlation, especially in the first and second stages. What’s more, at each of the precipitation process time, the positive abnormal apparent heating source (Q1) and moist sink (Q2) were located in the rain band position. Meanwhile, there also had strong ascent motion, helping from heavy rain and severe floods in the MLYR. (4) The precipitation anomalies responded to El Nino with different durations was different from each other. On the whole, there were positive anomalies, the anomalies decreased with the duration shortens.It showed that the strong SSTA in the preceding autumn significantly affects the rainfall in June in the MLYR.(5) It is found that when the SSTA enhanced more than2℃, there had a positive anomaly over MLYR. In addition, the intensity of precipitation anomaly increased with that of the SSTA.(6) We constructed idealized SSTA based on the observational SSTA over the equatorial Pacific during September2009to June2010. The intensity of precipitation anomaly increased with that of the SSTA. When opposite SSTA were put in the model, the simulated results were different from the results of positive SSTA which are put in the model. It is showed that the model is not sensitive to negative SSTA.