Hello, did it rain today?

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.

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. These small water droplets will become raindrops and fall to the ground, and the volume will increase by about 1 10,000 times. How did these small water droplets increase their volume to more than 654.38+00,000 times? 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. 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 fall straight from the clouds to the ground and become our common rain.

The main component of rainwater is water (chemical formula H2O), and a small amount of sulfur dioxide (chemical formula SO2) and nitrogen dioxide (chemical formula NO2). Usually, the PH value of rain is around 5.6, and rain with a PH value less than 5.6 is acid rain. In thunderstorm weather, rain will contain a small amount of ozone molecules (caused by lightning), as well as various impurities and floating dust in the air.

Meteorology stipulates that the rainfall within 24 hours is less than 10.0 mm, or the rainfall within one hour is less than 2.5 mm, which 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. Rainstorm occurs when the rainfall is less than 50.0~99.9 mm or more than 16.0 mm within 24 hours ... If the rainfall is less than 100.0~ 199.9 mm within 24 hours, it reaches or exceeds 200.0 mm, which 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.

I hope it can help you solve the problem.