What are the natural causes of drought in Yunnan in winter and spring?

Mainly because of the landform of Yunnan.

1, Yunnan is a mountainous plateau, in which the middle altitude area of1000-3500m accounts for 87.2 1% of the province's land area, and most of Yunnan Province is located in the middle altitude area.

2. Yunnan's climate basically belongs to subtropical plateau monsoon type, with obvious three-dimensional climate characteristics, many types, small annual temperature difference, large daily temperature difference, distinct dry and wet seasons, and abnormal vertical temperature change with terrain height.

3. In winter and spring, Yunnan is mainly influenced by the easterly airflow from the continental high front or the westerly airflow passing through the south side of the Qinghai-Tibet Plateau, resulting in scarce precipitation and dry climate in dry season. Yunnan is in the dry season every winter and spring, with scarce natural precipitation and large evaporation, which is prone to meteorological drought.

4. Northwest Yunnan has a cold climate, long winter without summer and short spring and autumn; The eastern and central parts of Yunnan belong to temperate climate, with four seasons such as spring and winter when it rains; The south and southwest of Yunnan belong to the low-heat valley area, and some of them enter the tropical area south of the Tropic of Cancer, with long summer without winter and rainy to autumn.