How is the occlusal front formed?

When the warm air mass, the cold air mass and the cold air mass meet, two fronts are formed first, and then one of them catches up with the other, that is, an occluded front is formed. The front is blocked by mountains and the terrain is blocked, which is very common in China; Either the cold front catches up with the warm front, or two cold fronts meet head-on to form a shelter. They force the warm air in front of the cold front to leave the ground and get trapped in the air. We call the interface between the cold air mass behind the cold front and the cold air mass in front of the front a blocking front. When the cold front catches up with the warm front, an occluded front is formed. Before the satellite cloud image appeared, it was difficult to determine the sheltered front. The satellite cloud image clearly shows the blocked front.

Meteorologists' theoretical research on frontier matured in the early 20th century. They believe that the most intense weather in the atmosphere does not occur in the cold and warm air mass, but on the interface of the cold and warm air mass. Meteorologists define the front as: cold and warm air masses meet in space, and the narrow transition zone with discontinuous meteorological elements between them is called the front. The interface is called the front, and the intersection of the front and the ground is called the front. In practical work, front and front are collectively referred to as front. The front is always inclined in space, and it is inclined to the side of the cold air mass. Warm air is above the front and cold air is below the front. The length of the front line is several hundred to several Qian Qian meters, the horizontal width near the ground is about several tens of kilometers, the altitude can reach more than 200 to 400 kilometers, and the vertical thickness is several hundred meters to one or two kilometers.

There are three main conditions for the formation of the blocking front: the terrain blocking formed by the front being blocked by the mountain; Two cold fronts meet head-on; The cold front in temperate cyclone catches up with the warm front; In these cases, the warm air in front of the cold front is lifted off the ground and trapped in the air. Therefore, the interface between the cold air mass behind the cold front and the cold air mass in front of the warm front is called the blocking front.

There are many ways to classify fronts, and the most commonly used ones are divided into cold fronts, warm fronts, quasi-static winds and blocking winds according to the movement of fronts.

There are three kinds of blocking fronts: warm blocking fronts, where the cold air mass in front of the warm front is colder than that behind the cold front; The cold air mass behind the cold front is colder than that before the warm front. There is little difference in air mass properties before and after neutral blocking front and blocking wind.