How is the rainfall forecast calculated?

Rain falls from the sky to the ground without evaporation, infiltration and loss. The depth of the 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 tube and measuring cup. The diameter of the rain tube is generally 20 cm, and there are funnels and bottles inside. The measuring cup has a diameter of 4 cm and is used in conjunction with the rainfall cylinder. When measuring,

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. In Yan 'an, Shaanxi, where there is little rain, it is called rainstorm when the daily rainfall reaches more than 30 mm.