Urgent. ! ! Main meteorological disasters and their occurrence frequency in northern China.

This is a major meteorological disaster in China. Drought is widely distributed, not only in rainy areas but also in semi-arid areas. Drought is most frequent in North China, Loess Plateau, Hexi Corridor and Sichuan Basin.

Heavy rain; rainstorm

It is one of the major meteorological disasters in China. China is one of the countries with more rainstorms in the world, with concentrated rainfall and high intensity. Especially in the summer in northern China, rainfall often reaches or exceeds the annual average rainfall within a few days.

Cold wave and freezing disaster

Cold wave: It is one of the major meteorological disasters in China. It is a strong cold air accumulated in high latitudes, which quickly invaded China southward, causing a wide range of severe cooling, accompanied by strong winds, rain and snow, freezing and other disasters. This weather process is called cold wave or strong cold air. Cold wave is the main meteorological disaster affecting China, which lasts from September to May of the following year, and the severe seasons are spring and autumn.

Freezing injury is also one of the main meteorological disasters in China. Can be divided into cold damage and freezing damage ┄ freezing damage: refers to the near-surface air temperature from 0? Above c suddenly dropped to 0? The average minimum temperature is lower than C, or it is lower than the multi-year average for a long time in winter or early spring, resulting in animal and plant casualties and economic losses. Freezing injury includes snow (snowstorm, white disaster), freezing rain (rain), freezing injury, ice accumulation and freezing injury. ┄ chilling injury: refers to the injury to crops when the ambient temperature is lower than the required temperature for their growth and development (but still above 0 degrees), which delays the growth period of crops and leads to the reduction of agricultural production. Cold damage includes low temperature damage, late spring cold, cold dew wind and so on.

High temperature dry hot wind

The summer temperature in China is obviously higher than that in the same latitude area, and high temperature is often a serious disaster.

Dry-hot wind is a special type of heat hazard, which is a comprehensive agrometeorological disaster combining high temperature and low humidity with certain wind power. Dry-hot wind generally appears in late spring and early summer in northern China, that is, from filling stage to wax ripening stage, which can reduce crop yield or quality.

White disaster and black disaster are serious natural disasters in winter in northern pastoral areas of China. White disaster is a disaster caused by excessive snowfall and burying pasture, which makes it impossible for livestock to eat grass. Black disaster is a disaster caused by too little snowfall and drought and no water.

White disasters in pastoral areas in China mainly occur from June 10 to April of the following year, especially in June 1 1 and March-April, which are frequent and harmful. The pastoral areas affected by it are mainly Inner Mongolia Plateau Pastoral Area, Qinghai-Tibet Plateau Pastoral Area, Northern Xinjiang Mountain Area and Qilian Mountain Pastoral Area. The black disaster mainly occurred in the waterless winter pasture in pastoral areas of China. This pasture can't be used because there is no water to drink during the growing season. It can only be used when stable snow forms in winter. Therefore, in the year when there is no snow or little snow, because livestock can't eat snow, grazing here will encounter disasters and form a black disaster. The pastoral areas where the Black Disaster occurred were mostly in the west of China.

In addition, there is dust in the north. ...

In recent years, due to the destruction of the natural environment and the abnormal use of chemicals (such as fluorine and various pesticides), some new meteorological disasters, such as acid rain and air pollution, have emerged. It has aggravated some existing meteorological disasters, such as greenhouse effect, urban heat island, El Ni? o and La Nina, high temperature heat wave and ultraviolet radiation.