Disasters affecting meteorology and climate in China
Summer drought: Generally speaking, summer drought refers to the phenomenon that the subtropical high moved northward to control the middle and lower reaches of the Yangtze River after the end of the meiyu in mid-July, resulting in long-term and large-scale hot and humid weather (high temperature weather) in this area. At this time, because the quasi-static front moved northward to the Yellow River basin, the middle and lower reaches of the Yangtze River were controlled by a single subtropical high, and downdraft prevailed, which made the weather hot and humid and the wind was generally small, which made people feel very uncomfortable. When the summer drought comes, we should do a good job in heatstroke prevention and cooling, minimize outdoor activities during the day, and inevitably take measures to prevent heatstroke and burns. At the same time, it is also the peak period of water and electricity consumption, and relevant departments should do a good job in water supply and power supply.
Typhoon: a tropical cyclone with a strong warm heart structure that appears in the western Pacific and South China Sea in summer and autumn. Most typhoons affecting China are generated in the South China Sea, east of the Philippines and near Guam. Because the surface seawater temperature in these areas is higher than 26 degrees and the thickness is larger (more than 60 meters), the tropical disturbance generated in these areas can absorb the heat and water vapor on the ocean surface, develop continuously in a suitable environment, and finally form a powerful tropical cyclone with a central warm core structure. The eastern coast of China, from Liaoning in the north to Hainan and Guangxi in the south, will be affected by typhoons, especially in Zhejiang, Fujian, Guangdong, Taiwan Province and Qiong, as well as Hong Kong and Macao. When typhoons affect coastal areas, the main disasters are storm surges (strong winds, heavy rains and storm surges), and the inland areas are mainly heavy rainfall. Therefore, the forecast and monitoring of typhoons should be strengthened, and coastal areas should do a good job in preventing storm surges, floods and geological disasters in inland areas.
Spring drought: Because the dry air from the mainland still controls the northern region in spring, spring drought usually occurs in the north, from March to May. At this time, due to the northward movement of the direct point of the sun, the surface temperature rises rapidly, but the surface air can only get heat from the surface but not the water vapor released from the surface, and the air is dry and difficult to cloud, resulting in rainfall. Although warm air is active at this time, it generally moves in the south and cannot reach the north, which also makes precipitation scarce and appear in this area. Spring drought is a common disaster in spring in northern China. After a long time, the surface water dried up and the surface cracked, making it difficult for people and animals to drink water. Therefore, making a good forecast, detecting weather changes in real time, saving water, implementing artificial rainfall and transferring water from south to north can alleviate the spring drought.
Summer waterlogging: Because most areas in China have monsoon climate and precipitation is concentrated in summer, summer waterlogging is the abbreviation of flood disaster caused by concentrated precipitation in summer, which generally occurs in June-September in the south and July-August in the north. Due to the characteristics of high intensity and different duration of precipitation in summer, monitoring, forecasting and taking various measures are the main defensive measures.
Late spring cold: As the cold air in spring still has a certain intensity and continues to go south, the cold air force is strong in some years, resulting in the spring temperature being seriously lower than the annual average. Generally speaking, March is the worst season of late spring cold. Because it is early spring and the cold air is still very strong, frequent southward movement will lead to a drop in temperature and a cold spring. The northern region is more important than the southern region, and the frequency of occurrence is higher. Because now is the season when winter wheat begins to grow and fruit trees begin to blossom, the late spring cold will seriously affect the growth of crops, and the heavy snow and late frost in spring will even cause crop death, thus causing serious losses. Therefore, it is necessary to make a good forecast and strengthen anti-freezing measures.
Cold wave: it refers to the phenomenon that the temperature in this area drops by more than 10 degrees and the lowest temperature is lower than 5 degrees within 24 hours due to the influence of strong cold air. This strong cold air can be called a cold wave. China will be affected by the cold wave except the South China Sea islands, but the north and the middle and lower reaches of the Yangtze River are more frequent areas. Because most of the cold waves affecting China come from the Arctic Ocean, the Western Siberian Plain and the Mongolian Plateau, these areas are cold in winter, which makes the ground air contract and the air pressure increase when it is cold. Under suitable conditions, these extremely cold air will affect most parts of China southward, thus forming a cold wave. When the cold wave affects, strong north wind and cooling, as well as frost and precipitation (thunderstorm, rainstorm and blizzard) will all cause disasters, so it is very important to make a good forecast and take various warm-keeping measures to prevent heavy snowfall.
Sandstorm: It usually occurs in northern China in spring. It is a phenomenon that large particles settle when the wind weakens, because the wind rolls the dust and soil on the exposed surface into the sky. Due to the bare surface in spring, frequent winds, scarce precipitation and loose soil, it is easy to be blown to the sky by the wind. Large particles will settle when the wind weakens, and small particles will enter the high altitude and reach far away with the high-altitude airflow. Because the air quality will be greatly reduced when the sandstorm strikes, it is an effective measure to protect individuals and equipment, make a good forecast and cover the ground with vegetation to reduce the impact of sandstorm.
Rainstorm: Except in desert areas and extremely cold areas, rainfall with 24-hour precipitation reaching or exceeding 50 mm will occur all over the country, which is distributed in all seasons, but concentrated in summer, and frequently occurs in areas affected by monsoon. The main defensive measures are drainage, strengthening forecasting and preventing secondary disasters.
Flooding: China's distribution area is second only to drought, which is a natural disaster. It is excessive precipitation that causes surface water to overflow and accumulate water. In China, floods will occur in other areas except desert and alpine regions. Strengthening the detection of river water level, making a good forecast of heavy rainfall and preventing secondary disasters are the main protective measures.
Drought: Natural disasters with the greatest impact, the widest distribution area and the most serious losses in China are generally caused by long-term lack of effective precipitation. Drought may occur all over the country, especially in the northern region, and sometimes there will be drought in autumn, winter and spring, and drought all year round. According to the drought area and degree, making a good forecast, taking water-saving measures, implementing water resources scheduling and making full use of it, and carrying out artificial rainfall under suitable conditions are the main protective measures.