In the summer, some desert regions often experience strong winds. The swirling wind blew dust, trash, grass, and paper flipped into the sky, creating vertical eddies. They suddenly appeared, suddenly disappeared. It was given a mystical name – “demon wind.” It is a common weather phenomenon in meteorology called “dust sweeping wind.”
Dust-sweeping winds form in the condition afternoon in the summer, cloudy weather, high temperature, low humidity, and low wind speed. At that time, the sun shone strongly, and the ground temperature increased rapidly, the temperature of the soil layer was not uniform, the air layer near the ground was not stable. It was easy to produce intense convection movement, forming an empty column hot air has a certain thickness.
The area where it appears becomes the low-pressure zone. The surrounding high-pressure zone would rush in to fill the low-pressure zone, but under the force of the Earth’s rotation, the flow of air flowing into the low-pressure area in the northern hemisphere often deflects to the right. The flow of air entering the low-pressure gas center will swirl in a counter-clockwise direction, forming a swirling air current. Sometimes, due to the special terrain such as hills, dunes, the incoming air flow has to run around or crawl up high, so it is often deflected. Furthermore, the airflow will form a dead angle. The air on both sides of the airflow will simultaneously hit the dead angle, creating a rising wind, which will generate vertical convection and change the horizontal direction. That meeting place will form a whirlwind column.
After forming a turbulent wind, the lower the central air pressure, the faster the vortex speed, plus the intense upward movement, so light objects are easily swept away. But the wind sweeps the dust once formed because the rapidly increasing wind speed causes the exchange between the low-pressure area to occur rapidly, causing the difference in pressure to decrease very quickly. Hence, it is only in an instant. The whirlwind eye was gone. So, a cyclone’s existence is very short, generally only for a few minutes, not more than ten minutes long.
