What are the main causes of many droughts and floods in China?

The seasonal distribution of precipitation is uneven, and the annual precipitation changes greatly.

The eastern part of China is a typical monsoon climate zone. Affected by the summer monsoon, the precipitation is mainly concentrated in July and August, and the seasonal distribution of precipitation is uneven. If the intensity of summer monsoon is unstable, it is easy to cause floods and droughts.

Climatic characteristics

1, the temperature is high all the year round, the annual average temperature is above 22℃, and the most Leng Yue in winter is generally above 16℃ for half a year. In Xishuangbanna, Yunnan and southern India, the alpine plateau in the north blocks the invasion of cold air to the south, so the temperature is relatively high in winter.

2. The dry and wet seasons are obvious, and the precipitation is concentrated in the rainy season, with a large amount of precipitation. Under the control of the dry northeast monsoon, there is little precipitation in winter, and the temperature is the coolest moment of the year. Generally, the average humidity is often between 50% and 75%, which is a dry and cool dry season. The summer half year is the hottest half year of the year, because the sun has begun to directly heat the northern hemisphere. After the arrival of the southwest monsoon, it is easy to produce various stagnation fronts, such as tropical cyclones produced by the ocean and thunderstorms caused by thermal convection in the afternoon. Rainfall has increased significantly, with occasional heavy rain. At this time, the average humidity generally falls between 75~ 100%, which makes people feel unbearable humidity.

The monsoon is extraordinary.

In the dry season, the northeast monsoon emitted by land high pressure flows into the equatorial convergence zone on the ocean. In the rainy season, the southwest monsoon from the subtropical high in the southern hemisphere flows into the Tal low.

4. Tropical cyclones prevail.

Synchronized with the "summer monsoon", tropical cyclones prevail from mid-May to mid-September every year. The Indian Peninsula and Indo-China Peninsula are typical and major areas of this climate. But the start and end times of the two seasons are different: the Indian Peninsula is usually rainy from June to September, and the dry season is 10 to May. In the late dry season (April-May), the weather is extremely hot, and the highest temperature is often above 40℃. The rainy season is full of rainfall, which often causes floods.

Extended data

Tropical monsoon climate is a climate type. The tropical monsoon climate is distributed in Southeast Asia from north latitude10 to the Tropic of Cancer, such as southern Taiwan Province Province, Leizhou Peninsula, Hainan Island and southern Yunnan. Indian zhina Peninsula; Most of the Indian peninsula; Philippines; Australia's northern coast and other places. Typical station: Cochin.

The tropical monsoon is remarkable here, and the seasonal variation of wind direction is obvious throughout the year. Under the control of tropical continental air mass (Tc), precipitation is scarce. However, when the equatorial ocean air mass (E) is controlled, there is abundant precipitation, tropical cyclone rain and annual precipitation, which is generally in 1500-2000mm and concentrated in June 6- 10/October (northern hemisphere). The annual maximum temperature is above 20℃, and the annual variation is about 3℃- 10℃, which is extremely short in spring and autumn.

References:

Tropical monsoon climate-Baidu encyclopedia