Why do cold and warm air meet to form rain? Can only cold air form rain?

Yes, cold air and warm air are defined by the difference in the horizontal direction of temperature. That is, the air in the low temperature area is called cold air. First, topographic precipitation

The moist airflow is blocked by the mountain and forced to rise along the windward slope, so the temperature drops and the water vapor in the air condenses, which is called topographic precipitation. When the airflow crosses the top of the mountain and flows down the leeward slope, it will become warmer and drier, and dry and hot winds will appear in some places. There are many mountains and the weather is changeable.

Second, convective rain

Convective rain prevails in tropical and temperate summer afternoons. Due to the high temperature and strong evaporation, the airflow rich in water vapor rises sharply. When it reaches high altitude, it cools into clouds and causes rain, which is called convective rain. It is characterized by high intensity, short rainfall time and small rain area, often accompanied by lightning and short-term strong wind, also known as hot thunderstorm, thunderstorm or thunderstorm. For example, the northwest rain in summer afternoon in Taiwan Province Province is (often in summer).

Third, it's raining ahead.

When air masses with different cold and warm properties meet, their contact surfaces are called fronts. Because of its low density, warm and humid air is lighter than dry and cold air, it will climb along the front and produce water vapor condensation rainfall, which is called front rain, such as plum rain in June in the south of the Yangtze River. It's raining in cold and warm fronts, and the cold front is raining before the front. Fourth, whirlwind rain.

Tropical cyclones appear on the tropical ocean surface, and their rainfall is mainly caused by the strong convergence of moist air at sea, also known as typhoon rain. The scope of tropical cyclone is smaller than that of temperate cyclone, but the clouds are dense and the airflow around the low pressure center is strong, which brings storms and often causes disasters. Tropical cyclones are called typhoons in East Asia and hurricanes in the United States. (There are many along the southeast coast of China)