Schematic diagram of frontal cyclones in the northern and southern hemispheres and obvious rainy weather

1. cold and warm fronts's judgment: In the frontal cyclone, to judge cold and warm fronts, we must first judge whether the cold air mass or the warm air mass moves actively. The conventional method is to judge according to the moving direction of the front at the groove line: as shown in the following figure, the direction of pressure gradient force (from outside to inside, from high pressure to low pressure, perpendicular to the isobar) is drawn at the dotted line, as shown by the arrow of line A; According to the deflection law of horizontally moving objects (in the northern hemisphere, for example, to the right), we can know that the movement direction of air mass is the direction indicated by the arrow on line B. By drawing, it is easy to judge that the dotted line A is the active movement of cold air mass on the north side, and it is a cold front. At the dotted line C, the warm air mass on the south side is active and is a warm front. The southern hemisphere's judgment method is similar. ?

2. Judging the precipitation area: the cold front precipitation is mainly behind the front, and the warm front precipitation is before the front. However, it is difficult to judge before and after the front, and it should be analyzed according to the moving direction of the front. The area that the front will pass through is in front of the front, and the area that the front has passed through is behind the front. There is also a rule here: the frontal precipitation is on one side of the cold air mass, which is the area of 1 and 4 in the figure. ?

3. The weather changes at the front crossing: rain, snow or windy weather occurs at the cold front crossing, and continuous precipitation occurs at the warm front crossing. A is a cold front. When crossing the border, the temperature drops, the air pressure rises, and there is rain, snow or windy weather. ?

4. Mistaken that there is a frontal anticyclone: After studying frontal cyclones, many students always think that there should be a frontal surface at the ridge of high pressure extended by high pressure, which will form a frontal anticyclone. In fact, the air in the low-pressure trough converges on the trough line, and the cold and warm air masses meet, so a front can be formed; At the ridge of high pressure, the air diverges from the ridge line, and the cold and warm air masses do not meet, so there will be no front.

Smart memory? The black triangle is cold, cool, rainy and windy. (cold front)?

Symbol semicircle is warm and harmonious, and continuous rainfall front is formed. (warm front)?

The circle line of the triangle is in the middle, and the rain moves slowly. (quasi-static front)

Induction? The quasi-static stop fronts affecting China mainly include the quasi-static stop fronts in South China, Jianghuai ("It rains a lot in Tomb-Sweeping Day" and "It rains in Huangmei Festival"), Kunming (there is no sunny day in Spring City and Guizhou) and Tianshan.

Warning? (1) Cold air mass and warm air mass are relative concepts, which are compared with the temperature of the area where the air mass arrives, so don't think that the temperature of the cold air mass must be low and the temperature of the warm air mass must be high. ?

(2) When cold and warm air masses meet on fronts, the warm air mass rises, which is easy to produce precipitation, but not all fronts may produce precipitation.