Rainfall can be divided into several grades.

Divided into six grades. Light rain, moderate rain, heavy rain, heavy rain, heavy rain, heavy rain.

Light rain: 1d (or 24h) rainfall is less than 10mm.

Moderate rain: 1d (or 24h) rainfall 10 ~ 25mm.

Rainstorm: 1d (or 24h) rainfall is 25 ~ 50mm.

Rainstorm: 1d (or 24h) rainfall 50 ~ 100mm.

Rainstorm: 1d (or 24h) rainfall 100 ~ 250mm.

Extraordinary rainstorm: 1d (or 24h) rainfall is more than 250mm.

Extended data:

Basic elements of rainfall

(1) Rainfall duration and rainfall time: Rainfall duration refers to the duration of a rainfall, that is, the time from the beginning to the end of a rainfall. Rainfall time refers to a long period of time corresponding to a certain rainfall, during which the rainfall is not necessarily continuous. Rainfall duration and rainfall time are in minutes and hours.

(2) Rainfall intensity: refers to the rainfall in unit time, and the unit is millimeter/minute or millimeter/hour. ..

(3) Rainfall area: refers to the horizontal area covered by a certain rainfall, and the unit is km2.

(4) Storm center: refers to the local area where the intensity of rainstorm is relatively concentrated.

There are many reasons for the rain, and the manifestations are unique, including Mao Mao rain, continuous rain and pouring rain. After the water on the earth is irradiated by sunlight, it becomes steam and is evaporated into the air.

Water vapor condenses into small water droplets when it meets cold air at high altitude. These small water droplets are very small, with a diameter of only 0.0 1 ~ 0.02 mm and a maximum of only 0.2 mm ... They are small and light, and are held up in the air by the updraft in the air. It is these small water droplets that gather in the air to form clouds.

It mainly relies on two means, one is condensation and sublimation. The second is to rely on the collision and increase of cloud droplets. In the initial stage of raindrop formation, cloud droplets mainly condense and condense themselves by constantly absorbing water vapor around the cloud.

If the water vapor in the cloud can be constantly replenished and replenished, so that the surface of the cloud droplets is often in a state of supersaturation, then this condensation process will continue, making the cloud droplets grow and become raindrops.

Rain usually occurs in four forms:

1. Front rain (plum rain): Warm and humid air from the ocean meets cold air from the land. Because cold air is heavy and warm air is light, warm and humid air is forced to rise and condense when it is cold, forming a long and wide rain belt. This is frontal rain.

2. Convective rain: In summer, under the strong sunlight, the warm and humid air in some areas rises sharply, and it condenses when it meets cold to form rain. This is convective rain, which is called "thunderstorm" in meteorology, and we usually call it "explosion". In addition, typhoon rain is also a kind of convective rain.

3. Topographic precipitation: Warm and humid air from the ocean is forced to rise when it meets mountains, and condenses when it meets cold, resulting in rainfall.

4. Typhoon storm: The hot and humid air on the tropical ocean surface rotates and rises strongly in a large range. In the process of rising, the temperature drops rapidly, and a large amount of water vapor condenses into clouds and rain, which is typhoon rain.

References:

Baidu encyclopedia-rainfall level