Why is it raining less and less?

Since 20 10, there has been a serious drought in southwest China, and the continuous high temperature and lack of rain have caused the drought in Yunnan, Sichuan, Guizhou, Guangxi and Chongqing to continue to worsen. Because of the lack of water, winter wheat is in an emergency, large and small livestock are in an emergency, and farmers' production and life are in an emergency. Not only industrial production water is in an emergency, but also urban water is in an emergency, and ecology is also in an emergency. Tens of millions of people have difficulty drinking water because of the subsidence of the airport runway.

But in my impression, Yunnan has four seasons like spring; Jiuzhaigou with water in Sichuan; There are Huangguoshu Waterfall and the famous Moutai in Guizhou. How can we make wine without water? Guangxi has the best scenery in Guilin and water. Chongqing is a foggy city, wet and watery, and now it's a bit puzzling to say that it is short of water and dry.

Huaxi newspaper provided the answer from Sichuan.

The reporter interviewed Ma Zhenfeng, a climate expert and director of Sichuan Climate Center, and made a detailed interpretation of this year's "drought" from the perspective of climatology.

Why did Southwest China do this this year? Ma Zhenfeng put forward three important reasons.

First, the plateau thermal factors of the Qinghai-Tibet Plateau. Sichuan Province is greatly influenced by the "roof of the world". Last winter, there was little snow on the Qinghai-Tibet Plateau, and the plateau thermal factors were good, which affected the drought in the whole province.

The second is the influence of El Nino phenomenon. Under this influence, the surface heat flow in the Pacific Ocean moved eastward, taking away tropical vapour band, which led to an increase in precipitation in eastern China. On the contrary, tropical water vapor decreases, and less water vapor enters the southwest from the south.

Third, the timing of cold air is not well grasped. Although the cold air has affected China many times this winter, most of the cold air began to move eastward in the north and directly "slipped" from the edge of Sichuan Province. Coupled with the Qinling Mountains, if the cold air is not "strong" enough to cross the mountains, it will still not affect the basin. Even if sometimes cold air enters the basin and forms the first condition of rainfall with warm air: convective weather, the second condition of rainfall cannot form precipitation without rich water vapor. "This is a process that requires cooperation."

Yunnan's explanation is like this.

Zhang Lei, a reporter from China Weather Network, interviewed Wang Xuefeng, deputy director of the Climate Center of Yunnan Meteorological Bureau, to interpret the recent drought.

Reporter: At present, the drought in most parts of the province is very serious. Please elaborate.

Wang Xuefeng: In terms of people's life or drinking water, central Yunnan may be much more serious, especially in Chuxiong, Qujing and northern Dali, but drinking water for people and animals in Simao may not be so serious. Kunming, Chuxiong and Qujing are the most serious places.

Reporter: Does it often happen that the rainy season ends early over the years?

Wang Xuefeng: The rainy season in Yunnan ended around the middle of 10, which is an average state. Every year is different, some are ahead and some are behind.

Reporter: Did the rainy season end the earliest in previous years?

Wang Xuefeng: Actually, it isn't. A little earlier than last year. This year's drought is not only the problem of the early end of the rainy season, but also the problem of less precipitation in the rainy season last year. In other words, before the rainy season passed, there was little precipitation, which mainly affected the storage of reservoirs and ponds, reservoirs and dams, and there was no water supply after the drought. In addition, the dams and ponds of Dudu Reservoir can be filled, but only half of them were filled in 2009. If they dry up later, the water in dams and ponds will dry up immediately. Those photos you saw are such places.

Reporter: What causes the abnormal rainy season and the decrease of precipitation?

Wang Xuefeng: This must be the result of abnormal atmospheric circulation. Although there is no direct causal relationship between global warming and drought, it is normal for extreme events to occur frequently after global warming. In other words, global warming will trigger extreme events, such as drought. But we are not sure whether there is a direct causal relationship between this drought and global warming.

Reporter: When is the drought expected to ease?

Wang Xuefeng: Judging from the current situation, a small amount of precipitation has no effect on alleviating the drought in Yunnan. From March 16 to April 15, the precipitation in Yunnan will not be too much, and March-April is a seasonal drought period in Yunnan, which is dry every year, especially this year. A small amount of precipitation can't alleviate this year's drought. For example, at a station in Chuxiong, the soil water content measured by 10 cm is already below 20%, which is a very small number. In agriculture, 60% is short of water. By 20%, everything has been done on the ground, everything has been done, and nothing can grow. So now it is estimated that the drought will last until early summer. However, it is uncertain whether it will be as dry as it is now, but there is a great possibility of continuous drought.

Reporter: When will the rainy season come this year?

Wang Xuefeng: Some places in the province are early and some places are late, but the fluctuation will not be too great. Whether it is early or late, we have to wait until mid-May, which is not much different from previous years.

Reporter: Will the rainy season alleviate the drought?

Wang Xuefeng: Once the rainy season comes, the drought will definitely be alleviated. Because of the heavy rainfall in Yunnan, there is no shortage of water in general, and the average precipitation is1000 mm. The problem in Yunnan is uneven seasonal distribution. The rainfall in the rainy season accounts for 85% of the total rainfall, and only 15% in the dry season. So when the rainy season comes, the drought can be lifted. The drought is unlikely to be completely relieved before the rainy season comes.

Reporter: Is there any place in the province that has not been affected by the drought?

Wang Xuefeng: No, basically not, but to different degrees. However, due to the arrival of the rainy season near the Nujiang River in the northwest corner, the drought has basically been lifted.

I think it's mainly El Nino. The north has been short of water for ten years.

The basic feature of El Nino phenomenon is that the sea surface temperature along the Pacific coast rises abnormally, the sea water level rises, and a warm current flows southward. It turns cold water in the East Pacific into warm water, causing tsunamis and storms, causing drought in some areas and excessive rainfall in others.

At present, the cause of this phenomenon is still under investigation, and I think it is related to the enhancement of solar light and heat penetration caused by atmospheric damage (:) guess)

At the same time, the decrease of forest adaptability to human environment is also one of the reasons for drought.