Climate types in Taihu Lake basin

Taihu Lake basin is located in the mid-latitude area and belongs to the humid north subtropical climate zone. The climate has obvious monsoon characteristics and four distinct seasons. In winter, cold air invades, mostly northward, cold and dry; At the turn of spring and summer, warm and humid air flows northward, and cold and warm air flows encounter continuous rain, which is called "plum rain" and is easy to cause floods; Summer is controlled by subtropical high, and the weather is sunny and hot. At this time, it is often affected by tropical storms and typhoons, resulting in severe storms and strong winds. The annual average temperature in the basin is 15℃- 17℃, which gradually increases from north to south. The annual average rainfall is 1 18 1mm, of which 60% is concentrated in May-September. Rainfall varies greatly every year, and the ratio of the maximum value to the minimum value of annual precipitation is 2.4 times. However, the annual runoff varies greatly from year to year, and the ratio of the maximum annual runoff to the minimum annual runoff is 15.7 times. Due to the influence of climate zonal change, the zonal soils in hilly and mountainous areas of Taihu Lake Basin are subtropical yellow brown soil and subtropical red soil. There are three types of non-zonal soil, among which saline soil in coastal plain is distributed in the north bank of Hangzhou Bay and the eastern plain of Shanghai, and meadow soil in alluvial plain is distributed in the vast alluvial plain along the river; Marsh soil is distributed in the lowlands along the Taihu Lake Plain. Farming soil is mainly paddy soil. The natural vegetation in Taihu Lake Basin is mainly distributed in hilly areas. The existing natural vegetation in hilly and mountainous areas, from north to south, the composition and types of vegetation are becoming more and more complex, and the evergreen tree species are gradually increasing. The northern part is a mixed forest of deciduous and evergreen broad-leaved forests in the north, and there are subtropical evergreen broad-leaved forests in Yili Mountain and Tianmu Mountain, but there are many deciduous trees in the evergreen broad-leaved forests in Yili Mountain, which is different from the typical evergreen broad-leaved forests.