What is the dry and hot wind like?

In early summer, high temperature and low humidity winds often appear in some parts of China, which generally last for about 3 days. Some areas are called "hot air", while others are called "fire wind" and "dry wind". Meteorologically, the comprehensive phenomenon that the temperature is higher than or equal to 25℃, the relative humidity is lower than or equal to 30%, and the wind speed is greater than or equal to 4 ~ 5m/s is called dry-hot wind.

Due to the different natural conditions in different places, the causes of dry and hot wind are also different. In the early summer of each year, the climate in the northwest inland area is hot, the precipitation is scarce, the temperature rises strongly, and the air pressure drops rapidly. A strong continental thermal depression often forms in western Mongolia and Hetao of China, as well as Xinjiang and Gansu. Around this hot low pressure, the pressure gradient increases with the increase of air mass temperature, so the dry-hot airflow rotates around the hot low pressure to form dry-hot wind, which is dry-hot wind. When the heat and low pressure leave the source, it will become drier and drier after passing through the dry and hot Gobi desert along the way, and the dry and hot wind will become stronger. Because of its high temperature, drought and strong wind, the strong dry-hot wind forces the evaporation of air and soil to increase, and the water consumption in crops is accelerated, thus destroying chlorophyll, hindering the photosynthesis and synthesis process of crops, and making plants wither rapidly from bottom to top, which can cause harm to local wheat, cotton, melons and fruits.

In the Huanghuai Plain, the late spring and early summer are the seasons when the solar altitude angle in the northern hemisphere increases, and it is also the sunny and rainy period before the rainy season in northern China. Under the control of the dry air mass, it is sunny, dry and windy here, and the ground temperature rises rapidly, with the average maximum temperature reaching 25 ~ 30℃. There is little chance of rain caused by clouds, and it is easy to form dry and hot wind.

The dry-hot wind in the Jianghuai Basin is produced under the influence of the southwest airflow west of the Pacific subtropical high. The Pacific subtropical high is a deep warm and high pressure system, which consists of warm air from the ground to the sky. During spring and summer, this high pressure stayed over the Jianghuai Basin and then gradually moved northward. Because in the high pressure area, the wind blows clockwise, so in the west of the Pacific subtropical high, the southwest wind blows. Located in the north and west of subtropical high, affected by this southwest wind, it produces dry and hot wind weather. Dry hot wind often harms crops together with drought. In the drought period, the roots of crops can't absorb the proper water, and the dry and hot wind takes away a lot of water from the stems and leaves, thus speeding up the withering and death of crops.

In the plain area of the middle and lower reaches of the Yangtze River, the weather is sunny and dry after the rainy season, and the dry hot wind in the south is often accompanied by "summer drought", which is not conducive to heading and flowering of double-season early rice.