The weather forecast usually says "rainfall 100 mm" What do you mean, how many millimeters are there?

It means that the rainfall of 1 hour per square centimeter is * * mm, and generally more than 30 mm may cause floods. Of course, it depends mainly on different regions.

What is rainfall?

Rain falls from the sky to the ground without evaporation, infiltration and loss. The depth of water layer accumulated on the water surface is called rainfall (in millimeters), which can directly indicate the amount of rainfall.

At present, the commonly used instruments for measuring rainfall are rainfall cylinder and measuring cup. The diameter of the rain tube is generally 20 cm, and it is equipped with a funnel and a bottle. The measuring cup has a diameter of 4 cm and is used together with the rainfall tube. When measuring, pour the rainwater in the rainfall cylinder into the measuring cup, and you can know the rainfall of the day according to the scale on the cup.

According to the regulations of China Meteorological Bureau, the rainfall within 24 hours is called daily rainfall, and any daily rainfall below10mm is called light rain,10.0-24.9mm is moderate rain, 25.0-49.9mm is heavy rain, 50.0-99.9mm is rainstorm, and100.0-250. Due to the vast territory of China, a few regions have other regulations according to the specific conditions of Guangdong Province. For example, in rainy Guangdong, if the daily rainfall exceeds 80 mm, it is called rainstorm; In Yan 'an, Shaanxi, where there is little rain, it is called rainstorm when the daily rainfall reaches more than 30 mm. (

Rainfall: refers to the total amount of rain, snow, hail, etc. Dew, frost, etc falling from the atmosphere. Condensed by water vapor, in millimeters.

Rainfall intensity: refers to the rainfall per unit time. In millimeters per minute or millimeters per hour. The rainfall intensity standards generally adopted by meteorological departments in China are: light rain: 12 hours with rainfall less than 5 mm, or 24 hours with rainfall less than 10 mm; Moderate rain: the rainfall within 12 hours is 5- 14.9mm, or the rainfall within 24 hours is10-24.9 mm; Rainstorm: 12 hour rainfall 15-29.9mm, or 25-49.9mm within 24 hours ... The quantitative standard of rainstorm varies from place to place, depending on the specific situation. Meteorologically, rainstorm is roughly divided into three levels according to its intensity: rainstorm: 12 hour rainfall is equal to or greater than 30mm, or 24-hour rainfall is equal to or greater than 50mm rainstorm: 12 hour rainfall is equal to or greater than 70 mm, or 24-hour rainfall is equal to or greater than 100 mm; Extraordinary rainstorm: 12 hour rainfall is equal to or greater than 140mm, or 24-hour rainfall is equal to or greater than 250mm.

How to measure rainfall?

Rain falls from the sky to the ground without evaporation, infiltration and loss. The depth of water layer accumulated on the water surface is called rainfall (in millimeters), which can directly indicate the amount of rainfall. At present, the commonly used instruments for measuring rainfall are rainfall cylinder and measuring cup. The diameter of the rain tube is generally 20 cm, and it is equipped with a funnel and a bottle. The measuring cup has a diameter of 4 cm and is used together with the rainfall tube. When measuring, pour the rainwater in the rainfall cylinder into the measuring cup, and you can know the rainfall of the day according to the scale on the cup.

According to the regulations of China Meteorological Bureau, the rainfall within 24 hours is called daily rainfall, and any daily rainfall below10mm is called light rain,10.0-24.9mm is moderate rain, 25.0-49.9mm is heavy rain, 50.0-99.9mm is rainstorm, and100.0-250. Due to China's vast territory, a few areas have other provisions according to the specific conditions of this province. For example, in rainy Guangdong, if the daily rainfall exceeds 80 mm, it is called rainstorm; In Yan 'an, Shaanxi, where there is little rain, it is called rainstorm when the daily rainfall reaches more than 30 mm.

Don't worry if you don't have a rain cone at hand. You can make one by yourself with some commonly used utensils, and the effect is quite good. Take a disposable plastic or paper bowl with a diameter of 20 cm (you can choose a convenient paper bowl with a suitable size), cut a small hole slightly larger than corn kernels at the bottom, and then put the bowl on a pot without a cover. There is a glass bottle in the jar, and the bottle mouth is connected with the small hole in the bottom of the bowl. The simple rain tube is ready. After the simple rainfall pipe is completed, it can be placed 70 cm above the ground (the distance between the nozzle and the ground) to receive rainwater. After the rain stops, weigh the water in the bottle with a scale. 30 grams of water is equivalent to 1 mm of rainfall.