Detailed explanation of climate in Huaihe River basin

Huaihe River Basin is located in the transitional zone between north and south of China, with a warm temperate zone in the north and a subtropical zone in the south, with a mild climate and an annual average temperature of1-16℃. The temperature changes from north to south and from coastal to inland. The extreme maximum temperature is 44.5℃, and the extreme minimum temperature is -24. 1℃. The evaporation is just smaller than that of Peking University, with an average annual water evaporation of 900- 1500mm and a frost-free period of 200-240 days. Since ancient times, the Huaihe River has been the natural dividing line between the north and the south of China. The average annual precipitation in Huaihe River Basin is about 920mm, which decreases from south to north, with mountains more than plains and coastal more than inland. There are three high precipitation areas in the basin: one is Funiu Mountain area, with an average annual precipitation of more than 1000mm; Second, Dabie Mountain area, 1400mm or more; ; The third is the downstream offshore area, which is above 1000 mm, and the precipitation in the northern part of the basin is the least, which is below 700 mm. The precipitation changes greatly during the year, and the maximum annual rainfall is 3-4 times of the minimum annual rainfall. The annual distribution of precipitation is also extremely uneven, and the precipitation in flood season (June-September) accounts for 50%-80% of the annual precipitation. Typhoon (including typhoon inverted trough), vortex shear, north-south shear and cold shear line are the weather systems that produce heavy rain in Huaihe River basin, and the first two are mostly. Vortex shear type is the main type in the early rainy season, and typhoon is involved in the later rainy season. The typhoon track covers the whole basin. The trend of rainstorm is generally consistent with the movement of weather system, and the center movement of typhoon rainstorm is related to the typhoon path. Cold peak rainstorm usually moves from northwest to southeast, and vortex rainstorm usually moves from southwest to northeast. With the intersection of north-south airflow, the shear line or front swings north-south, southeast and northwest, and the rainstorm center moves with it. For example, in July of 1954, several heavy rains were caused by the vortex shear line. The rainstorm first appeared in the mountainous area of Huainan, then advanced to the Hongru River and Sha Ying River basin in the northwest, then moved eastward to Huaibei area, and finally disappeared in northern Jiangsu. A precipitation process affected the whole Huaihe River basin. Because the direction of rainstorm is close to the direction of river, the Huaihe River basin is prone to floods. Huaihe river basin is located in the transitional zone between north and south of China, belonging to the warm temperate semi-humid monsoon climate zone, which is characterized by drought in winter and spring, sultry and rainy in summer and autumn, drastic changes in temperature and cold, and early flooding. The annual average temperature 1 1 ~ 16℃ increases from north to south and from coastal to inland. The monthly average maximum temperature is around 25℃, which appears in July. The monthly average minimum temperature is 0℃, which appears in 65438+ 10 month. The extreme maximum temperature can reach above 40℃, and the extreme minimum temperature can reach -20℃. The average annual rainfall in Huaihe River Basin is 965,438+065,438+0 mm, and the general trend is that the south is small in the north, the mountains are large, the plains are small, the coast is large and the inland is small. The annual rainfall in the upper reaches of Pi River in Dabie Mountain area of Huainan is the largest, which can reach more than 1500mm, while the northwest area adjacent to the Yellow River is less than 680mm. Although the Yimeng mountain area in the northeast is located in the northernmost part of the basin, the annual rainfall can reach 850 ~ 900 mm due to the terrain and the sea. The flood season is from May 15 to September 30, with an average rainfall of 578mm, accounting for 63% of the total annual rainfall. The annual rainfall varies greatly, with 1954, 1 185mm and 1 18 1mm at 1966, 1978 respectively.