Causes of drought in Yunnan

Global warming and the intensification of El Ni? o in the Pacific Ocean have destroyed the atmospheric structure, resulting in the inability of the ocean monsoon to land and form rainfall, which is the main reason for this extreme drought.

Yunnan is located in the southwest monsoon region in summer, and the precipitation is mostly related to the water vapor in the Bay of Bengal and the Indian Ocean. Because the Qinghai-Tibet high is too strong this year and extends eastward and downwards, the water vapor in the Bay of Bengal cannot be transported to Yunnan. In addition, Yunnan is mountainous, and the foehn effect intensifies the drought. "Another feature of Yunnan's climate is that the dry and wet seasons alternate obviously. 1 1 month is the dry season, and May to1month is the rainy season. Generally speaking, the rainy season accounts for more than 80% of the annual rainfall, so once the rainy season is insufficient, it may lead to drought all year round.

El Nino phenomenon: El Nino phenomenon, also known as El Nino flow, is a climatic phenomenon caused by the eastward shift of Walker circulation circle, which leads to the imbalance between the ocean and the atmosphere in the Pacific equatorial belt. Under normal circumstances, the monsoon air flow in the tropical Pacific moves from America to Asia, keeping the surface of the Pacific Ocean warm and bringing tropical rainfall around Indonesia. However, this pattern is disturbed every 2-7 years, and the wind direction and ocean current are reversed. The heat flow in the surface of the Pacific Ocean turns eastward to America, and then takes away tropical rainfall, resulting in the so-called "El Ni? o phenomenon". This phenomenon is essentially driven by ocean dynamics, and the corresponding atmospheric change is determined by sea surface temperature (in turn, atmospheric change will strengthen the distribution pattern of ocean temperature), and the distribution of sea surface temperature is determined by ocean dynamics, so the El Ni? o phenomenon represented by the above simplified model is predictable in nature. The whole process of El Nino is divided into occurrence period, development period, maintenance period and attenuation period, which generally lasts for about one year, and the change of atmosphere lags behind the change of seawater temperature. El Nino phenomenon generally refers to the climate anomaly caused by the rise of surface seawater temperature in the eastern Pacific near the equator. El Nino is not an isolated phenomenon, but a product of the interaction between tropical ocean currents and the atmosphere.