When did the Southwest drought start?

The 2010 Southwest China Drought was the worst drought that occurred in 2010 in five provinces and cities in southwest China, Yunnan, Guizhou, Guangxi, Sichuan and Chongqing. In some places, the drought can be traced back to July 2009, and by March 2010, more than 50 million people were affected. In Guizhou province alone, 3.1 million people are in need of relief due to the severe damage caused by the disaster. In the same month, the drought spread to western Hunan.

The worst drought in the southwest since meteorological data began. The reason for the drought is low precipitation and high temperature, and the two causes work together, plus it lasts for a long time The climate of Yunnan, Guizhou and other southwest regions is characterized by a clear rainy season and a dry season. Last year, there was very little precipitation during the rainy season, and the precipitation gradually stopped after August, which means that the rainy season ended early.

Since then, the precipitation has been low, and compared with the same period in history, Yunnan and Guizhou are the lowest in history.

In contrast, during these 200 days, the average temperature was 1 to 2 times higher, and compared with history, Yunnan had the highest temperature in history during the same period, and Guizhou ranked third.

The drought in the southwest began late in the Spring Festival, specifically in late February; Probably in Guizhou, Yunnan, Guangxi and other areas in southwest China (the drought in these provinces is relatively serious); The general situation of the drought is as follows: it is particularly difficult for people and livestock to drink water in the affected areas, the land has dried up, and the growth of crops has been affected.

Since the autumn and winter of '09, the rainfall has been lower than usual, and the temperature is higher than usual. Drought is a chronic phenomenon, and the longer it drags on, the more harmful it becomes. It has been about eight months after the continuous severe drought in the five southwestern provinces and cities of Yunnan, Guizhou, Sichuan, Guangxi and Chongqing.

Among them, Yunnan has a drought in autumn, winter and spring, and there is a drought once in a century, and Guizhou has a drought in autumn and winter, and there is a drought in 80 years.

Last fall.

I guess so.

Last fall, something happened back then.

Under the premise that the current climate warming is the background, extreme weather and climate events are more likely to occur.

The first is the influence of plateau thermal factors on the Qinghai-Tibet Plateau. The southwestern provinces are greatly affected by the "roof of the world", the Qinghai-Tibet Plateau had less snow last winter, and the thermal conditions of the plateau were good, resulting in a weak Indo-Myanmar trough, a weak South Asian monsoon, and insufficient water vapor transported to the southwest of China.

The second is the impact of El Niño. Under this influence, the sea surface temperature in the eastern equatorial Pacific Ocean is warmer, the subtropical high is stronger overall, and the water vapor carried by the East Asian monsoon meets the cold air from the north to the south, resulting in more precipitation in the eastern part of China and frequent snowfall in the north. On the contrary, the southwest region of China is dominated by downdrafts, and there are often sunny and sunny weather.

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Third, the timing of cold air has not been mastered. Although there have been several times of cold air affecting our country this winter, most of the cold air has begun to move eastward in the north, coupled with the relationship between the Qinling Mountains, if the cold air is not "strong" enough to climb the mountains, it will still not be able to cause an impact. Even though sometimes cold air enters the region, with warm air forms the first conditions for rainfall

Convective weather. However, if the second condition for the formation of rainfall, "water vapor", is not abundant, it still cannot form good precipitation.

Sea and land location, monsoon factors: Southwest China is Chinese mainland, and the summer monsoon from the Pacific Ocean has brought less rainfall when it arrives. The same is true for the summer monsoon from the Indian Ocean, which is blocked by the Himalayas and Hengduan Mountains.

In addition, summer monsoon activity is erratic, and sometimes drought occurs.

Topographic factors: There are mountains and mountains near the southwest region, and it is in the first and second steps of our country, and the altitude is relatively high.

The southwest region due to the collision of tectonic plates. Causes the southwest to uplift. Formation of plateau areas. It is located in the Inner Mill Excavation Plateau. Ocean precipitation is difficult to reach.

There are also the following aspects.

1) The karst landform in southwest China is extensive, and there are many karst caves and dark rivers underground, which is not conducive to water storage.

2) The southwest monsoon was weak and failed to reach the southwest of China;

3) The climate is dry in spring, the water vapor content in the air is small, the solid condensation is insufficient, and there are no conditions for the formation of precipitation'

4) There are many geological disasters in this area, and the plates are active and faulty, which is not conducive to the construction of large reservoirs, and the reserves of water resources are insufficient.