Why is Yunnan dry?

The special geographical location, changeable climate and environmental influence and complex geological structure of our province are the three main natural factors that caused the drought in our province this year. 1 Yunnan is located in a special geographical position on the low latitude plateau, with an average elevation of about 2000 meters. It is located in the southeast of the Qinghai-Tibet Plateau, near the South China Sea and the Bay of Bengal. There is a monsoon climate and plateau topography, which is easy to form a "foehn effect". "Foehn effect" means that when humid air rises on windward slopes, water vapor condenses into rain, and when it reaches the top of the mountain, the air dries, and then sinks along leeward slopes, raising the temperature. At this time, the air becomes drier and hotter, especially because several mountains in the province are blocking the airflow, resulting in extremely low water content in the air, making it difficult to form effective rainfall. In addition, another important reason affecting the "extinction" of rain in our province is global warming and the increase of extreme weather conditions, especially the intensification of El Ni? o phenomenon in the Pacific Ocean. Since last autumn and winter, the atmospheric circulation in the Qinghai-Tibet Plateau has been obviously abnormal. A tenacious cold and high-pressure air mass is formed in the plateau area, and the pressure field strength blocks the warm and humid air flow from the Indian Ocean and the Bay of Bengal, while the cold air in the north is not easy to reach the hinterland of Yunnan-Guizhou Plateau in the southwest, and it is difficult for the cold and warm air flows to meet to form precipitation, so the precipitation is less. The complex geological structure of our province has become the internal cause of drought. There are many limestone and karst areas in Yunnan, and there are widespread problems such as the inability to store surface water and the low utilization rate of groundwater, and there is a situation that' water flows downwards and people worry about heights'. "。 Because the mountainous and semi-mountainous areas in our province account for 94%, the difference between the highest point and the lowest point is more than 6600 meters. The mountains are high and the valleys are deep, and the rainwater quickly collects in the rivers at the bottom of the valley along the terrain, which is difficult to use. In addition, the karst area of the whole province is 1 10000 square kilometers, accounting for 28% of the national territory. Most or all of the rainfall runoff in karst areas seeps into the ground, which makes it difficult to conserve surface vegetation, thus aggravating the drought in our province.