How is the number of millimeters of rainfall in a certain city measured or calculated in weather reports?

The depth of the water layer that accumulates on the water surface without evaporation, infiltration, or loss when rainwater falls from the sky to the ground is called rainfall (in millimeters), which can be expressed intuitively The amount of rainfall.

At present, commonly used instruments for measuring rainfall include rain gauges and measuring cups. The diameter of the rain gauge is generally 20 cm and contains a funnel and a bottle. The diameter of the measuring cup is 4 cm, and it is used together with the rain gauge. When measuring, pour the rainwater from the rain gauge into the measuring cup, and you can know the amount of rainfall that day based on the scale on the cup.

A straight barrel with the same thickness up and down is a rainfall barrel. Its diameter and height are determined by meteorologists through scientific experiments. Whenever it rains, the rainwater flows through the round hole on the top and into the glass in this bucket. Every 3 hours, take out the glass and pour it into the graduated rain cup. The amount of rainfall is calculated and then reported to the meteorological station. For example, it is equivalent to putting a cup outside on a rainy day. After the rain stops, measure the height of the water column in millimeters, which is what we call the millimeters of rainfall.

”