The gale in Nantong, Jiangsu Province has caused many casualties. Why does strong convective weather suddenly appear?

Current affairs On the evening of April 30th, there was hail and large-scale strong thunderstorm and windy weather in Nantong, Jiangsu. There are 66 automatic stations in the city, and the maximum wind force exceeds 10. This kind of strong convective weather is generally local, short in duration and difficult to control human resources. Extremely fast. Among them, tongzhou bay Sanyou Group reached 45.4m/s( 14 gale), Haimen Changbao Town reached 39.0m/s, Haimen Dongzao Port reached 38.2 m/s, Tongzhou Huanben Farm reached 37.9 m/s, and Qidong Dongyuan Beach reached 37.7 m/s; Hailstones with a diameter of1~ 3cm appeared in Chengdong Town and Dagong Town of Hai 'an, Shizong Town of Tongzhou and Rudong Sunshine Island. According to statistics, more than 3,000 people were affected by the disaster, among them, trees fell, telephone poles were broken, and strong winds were involved in the river and died 1 1 person. People were injured due to the disaster 102, and medical treatment is being organized.

The main reason for the sudden appearance of strong convective weather is the strong vertical movement in the air, which leads to weather phenomena, the most typical of which is the strong convective weather in summer afternoon: during the day, the ground constantly absorbs the short-wave radiation of the sun, the temperature rises, and the long-wave radiation is released to heat the atmosphere. When the air near the ground receives enough heat from the earth's surface, it will expand and reduce its density, and then the atmosphere will be in an unstable state. It's like oil and water in a water tank. When the less dense oil is at the bottom of the water tank and the water is at the top, there will be a strong upward movement, and finally the oil will float to the water surface.

In the same way, the hot air near the ground rises under the buoyancy, forming a rising hot and humid airflow. When it rises to a certain height, the water vapor contained in the air will condense into water droplets due to the temperature drop. When water droplets fall, they are picked up by stronger updraft, and so on. Small water droplets begin to accumulate and integrate into large water droplets until the upper air cannot support their weight, and finally they fall into the rain.

The main reason for the wide range and high frequency of strong convective weather in some areas is the abnormal cold air activity in the south, which frequently collides with wet airflow and is very unstable. This humid and warm atmosphere will produce strong vertical movement in the hot afternoon in summer, leading to strong convective weather. In addition, the upper air in the northern region is controlled by the strong northwest airflow, and the weather is fine during the day, the solar radiation is strong, and the near-surface temperature rises rapidly, while the vortex in North China is relatively stable, which often leads to cold advection southward, forming an unstable atmosphere with cold upper and warm lower in some areas, making these areas prone to strong convective weather.