How to distinguish between before and after, it is best to have

According to the movement of the air mass, the front can be divided into cold and warm fronts. The cold air mass is strong and actively moves to the warm air mass. Such a front is a cold front. The warm air mass is strong and moves to the cold air mass actively. Such a front is a warm front. The rain area of the cold front is behind the front, and the rain area of the warm front is before the front. Judging method: No matter the cold front or warm front, the rain area is close to the cold air mass. The diagonal line crossing the ground in the figure is the front line. Taking the front line as the boundary, combined with the moving direction of the front line, the front of the front line is the front, and the back behind the front line is the back. The left picture shows the weather map of the cold front, and the moving direction of the front is the moving direction of the cold air mass, that is, the cold front moves to the right, the warm air mass is in front of the front, and the rain area is behind the front (the right side of the front is the front and the left side of the front is the back). So the rain area of the cold front is behind the front. The picture on the right shows the weather map of the warm front, and the moving direction of the front is the moving direction of the warm air mass, that is, the warm front moves to the right, the rain area is in front of the front, and the warm air mass is behind the front (the right side of the front is the front and the left side of the front is the back). Therefore, the rain area of warm front is in front of the front.