Why is there less precipitation now?

China is roughly divided into four precipitation areas. Divided by precipitation line, from coastal areas to inland areas, the precipitation distribution decreases in turn.

The 800 mm precipitation line in coastal areas has the most precipitation.

Beijing, Tianjin, Hebei and Henan belong to the 400 mm precipitation area, and the precipitation is average.

Hubei, Hunan, Gansu and Guangxi are areas with 200mm precipitation, and the precipitation is relatively small. In some areas, due to the role of inland lakes, precipitation is relatively high. Sichuan is a mountainous area, which is influenced by topography and has abundant precipitation.

Xinjiang and Qinghai-Tibet Plateau belong to areas with equal precipitation below 200 mm, with the least precipitation.

Hebei belongs to temperate-warm temperate, semi-humid and semi-arid continental monsoon climate, which is characterized by cold and little snow in winter and hot and rainy in summer. It is windy and dusty in spring and crisp in autumn. The distribution of annual average precipitation in the whole province is very uneven, and the annual change rate is also very large. Generally, the average annual precipitation is between 400-800 mm, and two rainy areas are formed at the southern foot of Yanshan Mountain and the windward slope on the east side of Taihang Mountain. Zhangbei Plateau belongs to the inland, and the precipitation is generally less than 400 mm. In summer, precipitation often occurs in the form of rainstorm. 1On July 29th, 966, the rainfall in Zunhua was 327.9mm, which was the largest daily rainfall in the province. There is little precipitation in spring, and drought in spring and waterlogging in summer pose a great threat to agricultural production.

Since 1980s, the global temperature has obviously increased. 198 1 ~ 1990, the global average temperature increased by 0.48℃ compared with 100 years ago. The main reason for global warming is that humans have used a lot of fossil fuels (such as coal and oil) and released a lot of greenhouse gases, such as carbon dioxide, in the past century. Because these greenhouse gases have high permeability to visible light radiated by the sun and high absorption to long-wave radiation reflected by the earth, this is commonly called "greenhouse effect", which leads to global warming.

The consequences of global warming will redistribute global precipitation. Under the influence of La Nina phenomenon, the water temperature in the equatorial western Pacific Ocean is high, and the water evaporation increases, which leads to the abnormal meridional circulation in East Asia, which makes the northerly airflow prevail in northern China, while the warm and humid airflow in the southeast is relatively weak, and the cold air in the north moves southward rapidly, so that the warm and humid airflow in the south with a lot of water vapor cannot develop northward, which leads to the decrease of precipitation in the north and the rain and snow disaster in the south.