Main seasons and causes of drought in Beijing

Drought is the most extensive and serious meteorological disaster in China.

The concept of drought: it refers to an agricultural meteorological disaster that can not reduce production because of the low level of agricultural technology, dry air and lack of water in soil.

Types of drought:

1, classified by drought causes.

(1) soil drought

The soil moisture content is low, and the adsorption of water by soil particles makes it difficult for the roots of plants to absorb enough water in the soil to compensate for the consumption of transpiration, and the water budget in plants is unbalanced, thus affecting normal physiological activities and even causing drought.

(2) Atmospheric drought

Although there is a certain amount of available water in the soil, the air is extremely dry, the light is strong, the temperature is high, and the transpiration of plants is intensified, which makes the water make ends meet, and the water balance in plants is destroyed, leading to drought.

2. According to the dry season.

(1) Spring drought

The spring drought mainly occurs in March-May. At this time, the temperature in many places in North China, Northwest China and Northeast China rises rapidly in spring, with dry air, strong solar radiation, strong wind and strong evaporation. In these areas, winter precipitation is scarce, and it doesn't rain for a long time or the rainfall is obviously less, which is prone to spring drought.

(2) Summer drought

Solar radiation is strong, the temperature is high and the temperature is low, so soil evaporation and plant transpiration are very strong. If there is little rain or no rain for a long time, it is easy to cause drought.

(3) Autumn drought

The characteristics of autumn drought are similar to those of summer drought, but the intensity is slightly weaker. Autumn and summer mainly affect the filling maturity of summer sowing crops and some late-maturing spring sowing crops, and affect the sowing and emergence of overwintering crops.

(4) Winter drought

In winter, the continental dry and cold air mass controls the vast areas of China, with scarce precipitation, strong northwest wind, low temperature and low humidity, which is prone to winter drought.

Causes of drought: Drought is mainly caused by long-term control of high air pressure. High pressure often occupies a large space, so drought often affects a large area. The abnormal monsoon called "large-scale drought" is the main cause of drought in China.

Drought index: the standard of drought degree in a certain area is called drought index.

Temporal and spatial distribution characteristics of drought;

1, regional distribution characteristics of drought

Drought is generally distributed in the following four areas.

(1) northeast arid area

This area has high latitude, low temperature and short growth period of crops. Due to the influence of low pressure, the precipitation is relatively stable and the drought frequency is relatively low. The drought in most years belongs to general drought.

(2) Huanghuaihai arid area

This area is the largest arid area in China with less precipitation and great changes, and the number of droughts also ranks first in China.

(3) The Yangtze River Basin and the arid areas of South China

The drought in Hubei, Hunan, Jiangxi, Jiangsu, Anhui and most parts of Fujian, Guangdong and Guangxi is severe, especially in the eastern coast of Guangdong and the southern coast of Fujian.

(4) Arid areas in southwest China.

There is less drought in north-central Yunnan Province and south Xichang, Sichuan Province.

2. Temporal distribution characteristics of drought.

(1) Drought in Northeast China in spring and summer (2) Drought in Huanghuaihai region in spring, summer and autumn.

(3) Summer and Autumn Drought in the Yangtze River Basin (4) Autumn and Winter Drought in South China (5) Winter and Spring Drought in Southwest China.

Measures to resist, avoid and prevent drought

1, drought-resistant measures

(1) Increase revenue and reduce expenditure, and irrigate rationally.

(2) Selecting drought-resistant varieties and sowing drought-resistant.

(3) Tillage and mulch to conserve moisture and inhibit farmland evaporation.

(4) Rain in Yun Geng to alleviate the drought.

2. Measures to avoid drought

(1) Reform the planting system to avoid drought and get a bumper harvest.

(2) adjust sowing to avoid drought

(3) the waterway is impassable, and the dry road is not allowed.

(4) Transplanting seedlings to avoid spring drought

3. Drought prevention measures

(1) Build water conservancy and improve farmland capital construction.

(2) Deep ploughing to improve soil and enhance soil water storage capacity.

(3) Cultivate drought-resistant varieties and improve drought-resistant ability.

(4) Greening wasteland and improving ecological environment.