Explain the weather system that causes precipitation.

In common weather systems, there are three types of precipitation:

1. Cyclone (low-pressure system): As the updraft prevails in the low-pressure center, the temperature of the airflow drops during the ascending process, resulting in water vapor condensation and precipitation.

Frontal: including warm front, cold front and quasi-static front. Near the front line, the cold and warm air masses meet, and the warm air mass climbs along the front line because it is light. In the same process, the temperature drops, which leads to the condensation of water vapor and the formation of precipitation.

Third, frontal cyclone: in fact, it is to combine the first two systems into one.

(In fact, there are other processes that can also cause precipitation, such as artificial precipitation enhancement projects. But in middle school physical geography, it mainly involves these three weather systems)