How to define light rain, moderate rain, heavy rain, rainstorm and rainstorm?

According to the meteorological regulations:

If the rainfall is less than10.0mm in 24 hours, or less than 2.5mm in one hour, it is called light rain.

If the rainfall within 24 hours is less than 10.0~24.9 mm, or the rainfall within one hour is less than 2.6~8.0 mm, it is called moderate rain.

If the rainfall is less than 25.0~49.9 mm in 24 hours, or less than 8. 1~ 15.9 mm in one hour, it is called rainstorm.

When the rainfall within 24 hours is less than 50.0~99.9 mm, or the rainfall exceeds 16.0 mm, a rainstorm occurs. ..

If the rainfall within 24 hours is less than 100.0~ 199.9 mm and reaches or exceeds 200.0 mm, it is called a torrential rain.

When the precipitation is less than 0.05 mm or there is precipitation before observation, but it is not observed due to rapid evaporation, the precipitation should be recorded as 0.0 mm and cannot be omitted, because this is a rainfall process.

Floods and rainstorms: Floods and floods caused by torrential rains are rare natural phenomena. According to the way of rainfall, it can be divided into thunderstorm, topographic precipitation, typhoon rain and cyclone rain.

Extended data:

Rain is a natural precipitation phenomenon, which is caused by the disturbance of atmospheric circulation. It is an indispensable part of the earth's water cycle and the only way for almost all terrestrial plants far away from rivers to replenish fresh water. Raindrops fall from the sky, big and small, fast and slow. The water on the earth's surface evaporates and rises, and it cools to form rain. Rainwater is the most important fresh water resource in human life.

The water drops falling from the clouds and the water on the land and sea surface evaporate into steam. When the steam rises to a certain height, it becomes small water drops when it is cold. These small water droplets form a cloud, where they collide with each other and merge into large water droplets. When it is too big for the air, it will fall from the clouds and form rain.

Rain is the most important fresh water resource in human life, and plants thrive on the moisture of rain and dew. But the flood caused by rainstorm will also bring great disaster to mankind.

Rain usually occurs in four forms:

1, frontal 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.

When it rains, how do these small water droplets increase their volume to more than 1 10,000 times? Mainly by two means: one is condensation, and the other is the increase of cloud droplet collision.

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.

However, sometimes the water vapor content in the cloud is limited, and in the same cloud, the water vapor is often in short supply, so it is impossible to make every cloud droplet grow into a larger raindrop, and some smaller cloud droplets have to be merged into a larger cloud droplet. If there are water droplets and ice crystals in the cloud, the process of condensation and sublimation will be greatly accelerated.

When the cloud drops increase to a certain extent, due to the increasing volume and weight of large cloud drops, they can not only catch up with the slower small cloud drops, but also "swallow" more small cloud drops, making themselves stronger. When the big cloud drops get bigger and bigger until the air can no longer hold them, they will fall straight from the clouds to the ground, which becomes ordinary rain.

References:

Baidu encyclopedia-rain