Relationships Between Anomalies of Land-Sea Thermal Contrast in North Africa and Summer Flood and Drought Across the Jianghuai Region of China

The flood and drought across the Yangtze and Huaihe River (Jianghuai) areas are frequent in summer,especially in June and July. Therefore,predicting the summer flood and drought in the Jianghuai region is always one of the key topics concerned by meteorologists in China. Previous studies focused more on the skin temperature anomalies in a local area, and paid less attention to the connections between the anomalies of land-sea thermal contrast in remote continents and the summer flood and drought in Jianghuai areas of China. By using the US NCEP/NCAR monthly mean reanalysis data and the rainfall data at 743 stations in China, based on the interdecadal variation characteristics of the flood and drought index (FDI) during 51 yr (1954-2004) in the Jianghuai region of China in summer, the North African areas have been selected as the key regions for the correlation analysis. The results show that the surface temperature anomalies in the key regions have good continuity in winter, and the winter North Atlantic Oscillation (NAO) is perhaps one of the important factors that bring about the continuity of the anomalies. By a singular value decomposition (SVD) analysis between the skin temperature in the previous winter in North Africa and the summer rainfall in the Jianghuai region, it is found that when the North African continent is colder (warmer) and its northwestern sea is warmer (colder), the rainfall increases (decreases) in the Jianghuai region in summer generally. Further analysis finds that the anomaly of the surface temperature contrast between sea and land in North Africa has a good indication for the summer flood and drought in the Jianghuai areas of China. Therefore, a sea and land thermal contrast index (SLTCI) is defined to reflect the intensity of the large-scale land-sea thermal contrast. A positive correlation between the SLTCI in North Africa and the summer FDI in Jianghuai areas is identified, and it can well indicate the extreme flood and drought situations in the Jianghuai region of China