Details of dry hot wind

Dry-hot wind is also called "dry wind", which is commonly called "fire south wind" or "fire wind". One of agrometeorological disasters. A dry and hot wind that occurs in the warm season and causes damage to wheat grains during the milk maturity period.

In dry and hot wind, the temperature increases significantly, the humidity decreases significantly, accompanied by a certain wind, transpiration intensifies, and the root system can't absorb water, which often leads to insufficient filling of wheat, serious sprouting and even withering and death. China's North China, Northwest China and Huanghuai areas all appeared during the late spring and early summer. Generally, it can be divided into two types: high temperature and low humidity and heat exhaustion after rain, all of which are mainly caused by high temperature.

The meteorological indicators of dry-hot wind hazards are different from person to person, and the winter wheat and spring wheat are different, and they are also inconsistent among regions. Generally speaking, for high temperature and low humidity type: light dry hot wind means that the maximum daily temperature is greater than or equal to 29-34℃, and the wind speed is greater than or equal to 2-3m/s at 14 o'clock. Heavy dry hot wind means that the daily maximum temperature is greater than or equal to 32-36℃, the relative humidity is less than or equal to 2-3% at 14 o'clock, and the wind speed is greater than or equal to 2-4m/s at 14 o'clock. Heat-withered type after rain: there is a rainfall process within 1 days before wheat ripens, and it turns sunny and heats up after rain, and the daily maximum temperature reaches above 3℃ within 2-3 days.

causes

due to the different natural characteristics in different places, the causes of dry hot wind are also different. In the early summer of each year, the climate in China's inland areas is hot, the rainfall is scarce, the temperature rises strongly, and the air pressure drops rapidly, forming a powerful continental thermal depression. Around this hot low pressure, the pressure gradient increases with the increase of air mass temperature, so the dry and hot airflow rotates around the hot low pressure to form a dry and hot wind, which is dry and hot wind. Strong dry and hot wind can do harm to local wheat, cotton, melons and fruits.

Mongolia with dry climate, the west of Hetao in China, Xinjiang and Gansu are areas where continental thermal depression often occurs. After the thermal depression leaves the source, it will become drier and drier after passing through the dry-hot Gobi desert along the way, and the dry-hot wind will become stronger. Tarim basin, located in the center of Eurasia, has an extremely dry climate, and the "burning wind" generated after a strong cold front crosses Tianshan Mountain and Pamir Plateau often causes a large-scale dry and hot wind in the local area.

in Huanghuai plain, the main reason for the formation of dry-hot wind is based on the atmospheric drought in this area. The late spring and early summer is the season with the largest direct angle of the sun in the northern hemisphere, and it is also a sunny and rainy period before the rainy season in northern China. Under the control of dry air mass, it is sunny, dry and windy here, and the ground temperature increases rapidly (the average maximum temperature can reach 25-3 C), so there is less chance of rain caused by condensation clouds, which is easy to form dry hot wind. This dry and hot wind is not good for the later growth and development of wheat in this area.

in the jianghuai river basin, dry-hot wind is produced under the influence of southwest airflow in the west of Pacific subtropical high. The Pacific subtropical high is a deep warm high pressure system, which is composed of warm air from the ground to the sky. During the spring and summer, this high pressure stayed over the Jianghuai basin, and then gradually moved northward. Because in the high pressure area, the wind direction is clockwise, so in the west of the subtropical high, the southwest wind is blowing. Located in the northern and western parts of the subtropical high, affected by this southwest wind, it produces dry and hot wind weather. In the early summer, there was still cold high pressure in the north, which kept going south, weakened its power and changed sex; When it merged with the subtropical high, its power was strengthened, so that the fine weather continued to be maintained and the dry-hot wind became more obvious.

In the plain of the middle and lower reaches of the Yangtze River, the weather is sunny and dry after the rainy season, and the southerly dry-hot wind is often accompanied by "summer drought", which is not good for heading and flowering of double-cropping early rice (or middle rice).