Summary of geography knowledge points in senior two: common weather system

1 Common weather systems: frontal system (cold front, warm front), cyclone and anticyclone, frontal cyclone.

Front system: (cold and warm air mass refers to relative temperature)

Similarities between cold and warm fronts: cold air mass is under the front and warm air mass is on the front.

It rains on one side of the cold air mass (the cold front is called the back of the front and the warm front is called the front).

(1) cold front and weather: the cold air mass moves to the front of the warm air mass actively (extremely cold wave).

Weather changes: it is often cloudy, windy, rainy, and cooling. There is strong wind, bringing rain and snow, etc. ); After crossing the border, the air pressure rose, the temperature and humidity plummeted and the weather turned fine.

(2) Warm front and weather: The warm air mass moves to the front of the cold air mass.

Weather change: there will be continuous precipitation when crossing the border; After crossing the border, the temperature rose, the air pressure dropped and the weather turned fine.

Cold front is the main factor affecting the weather in China. Rainstorms in summer and cold waves in winter are cold front weather.

4 Low pressure (also called cyclone) and high pressure (also called anticyclone)

(1) Cyclone: The central airflow rises and it is easy to form rainy weather.

The horizontal airflow converges counterclockwise in the northern hemisphere (the four fingers of the right hand hold the horizontal airflow to converge, and the thumb up indicates that the vertical airflow rises), while the horizontal airflow converges clockwise in the southern hemisphere (the left hand).

(2) Anti-cyclone: the central airflow sinks and the weather is fine. (For example, dry weather in summer and crisp autumn in the Yangtze River valley)

The horizontal airflow diverges clockwise in the northern hemisphere (the four fingers of the right hand are slightly open, which means the horizontal airflow diverges, and the thumb is downward, which means the central airflow sinks), and diverges counterclockwise in the southern hemisphere (the left hand).

Frontal cyclone: Cyclone is low pressure. In the actual atmosphere, the low-pressure system often has a low-pressure trough extending in a certain direction along the center (just like the plastic circular washbasin we are using now is squashed), and a frontal system is formed on the low-pressure trough. Frontal and cyclone are a whole (no high pressure system)

Note: In the low-pressure system in the northern and southern hemispheres, learn to judge that the cold front is the initiative of the cold air mass and the warm front is the initiative of the warm air mass according to the direction of air convergence movement in the cyclone.