What is the difference between squall line and cold front weather, and what is the relationship with frontal cyclone?

"squall line" refers to the weather phenomenon that the wind direction changes suddenly and the wind speed increases sharply. When it appears, the temperature will drop and it will be accompanied by rainfall. Squall line is a linear mesoscale thunderstorm group, not a cold front weather.

the condition of squall line-two air masses with different characteristics collide with each other is a necessary condition for squall line. The most common situation is cold air mass collision, but sometimes dry air collides with wet air. In either case, there will be wind shear in the sky. When two adjacent winds are different in direction and speed, wind shear will occur. He can be the rising air leaving the cloud top.

Although squall line belongs to mesoscale weather system, its formation and development are related to a certain large-scale weather situation. Squall lines mostly appear behind the upper trough and in the south or southwest of the cold vortex; Sometimes it appears in the low-altitude southwest warm and humid airflow in front of the high-altitude trough and at the northwest edge of the subtropical high; A few squall lines are generated in the inverted trough or easterly wave at the front of the typhoon. According to the corresponding ground situation, most squall lines are related to frontal activities, mainly occurring in the warm area 1 ~ 5 kilometers before the ground cold front.

squall lines are generated in stratification with strong potential instability (see atmospheric static stability). This kind of unstable stratification is mostly caused by the superposition of cold advection in the middle or upper layer on the warm and humid airflow in the lower layer. Squall lines are also related to high-altitude rapids, which mostly occur in rapids or areas with large vertical shear of wind.