What is the reason for the sudden black weather in Shenyang?

Strong convective weather suddenly thickened the clouds. On that day, the last cloud in Shenyang reached 9 kilometers, twice as thick as normal cloudy weather. Such thick clouds have a strong shielding effect on sunlight.

The main reason of cloud thickening is closely related to strong convective weather. During strong convection, water vapor is continuously transported into the air from bottom to top, and strong convection occurs in the troposphere, which makes the water vapor extend upward and the thickness of clouds increase obviously. The severe convective weather in our province is mainly caused by the shear line crossing.

In meteorology, the shear line generally refers to the weather system on the isobaric surface at low altitude of 850 HPA or 700 HPA. On the shear line, the airflow often has horizontal convergence and upward movement, which is easy to produce rainy weather. Shear lines can appear all year round, but mostly in the late spring and early summer when cold and warm air is active frequently.

It is not surprising that this phenomenon happens almost every year.