Causes of drought in southwest China

The drought in southwest China this year shows no signs of easing. What caused such a long and extensive drought? Judging from the current situation, most climate experts believe that high temperature and little rain are the direct causes of drought, but what causes high temperature and little rain? There are different opinions about the reasons. Wang Jinsong, a researcher at Lanzhou Institute of Drought Meteorology, China Meteorological Bureau, said that since June last year, the Middle East and the Pacific Ocean have been continuously warming and in El Ni? o state, which affected the weakening of Indian monsoon and led to the occurrence of drought in southwest China. Since the autumn of last year, the weak southwest airflow and insufficient water vapor transport have caused less precipitation and higher temperature, which are the direct reasons for the continuous meteorological drought in Yunnan and other places. "High temperature and lack of rain are the most direct causes of drought in southwest China." Wang Yongguang, chief forecaster of the National Climate Center, said in an interview with the media that from the atmospheric circulation situation, the south branch trough has been weak since winter, and the warm and humid airflow from the southwest of the Indian Ocean is weak, resulting in insufficient water vapor supply. In addition, the climate in the south lags behind the El Ni? o phenomenon, and the southwest is prone to meteorological drought. Ma Zhenfeng, director of Sichuan Climate Center, believes that Sichuan Province is greatly influenced by the "roof of the world". Last winter, there was little snowfall on the Qinghai-Tibet Plateau, and the plateau thermal factors were good, which affected the drought in the whole province. In addition, due to the influence of El Nino, the heat flow in the surface layer of the Pacific Ocean moved eastward, taking away tropical vapour band, resulting in more precipitation in eastern China. On the contrary, tropical water vapor decreases, and less water vapor enters the southwest from the south. In recent years, drought has become the meteorological disaster with the highest exposure rate in China. Among the "Top Ten Weather and Climate Events in 2009" issued by China Meteorological Bureau, there are three events related to drought, namely "a rare autumn and winter drought in 30 years raided the northern winter wheat area", "the worst spring drought in 50 years troubled Inner Mongolia, Heilongjiang" and "a rare autumn drought in 50 years burned all over the southern land". At the beginning of this year, drought hit the southwest again. Are there the same climatic reasons or human factors at work behind some extreme weather phenomena? Gerald Mill, a senior scientist at the National Center for Atmospheric Research, said in an interview with this reporter that the climate itself contains many natural variables, such as drought, floods and storms. Is a natural part of the climate system. Sometimes people can attribute part of the climate to some naturally occurring phenomena, such as El Nino. But Mueller said that human-induced climate change needs long-term accumulation, and a specific drought or storm cannot be absolutely attributed to human-induced climate change.