What is the rainfall forecast of 50 mm?

The rainfall of 50 mm is the 24-hour cumulative rainfall of 50 mm, and the rainfall exceeding 50 mm is designated as rainstorm.

Rainfall is an important disaster data with chaotic characteristics. Different departments have different standards for the classification of rainfall grades.

1, meteorological department

Rainfall refers to the depth of the water layer that falls to the ground in a certain period of time, expressed in millimeters. The rainfall per unit time is called rainfall intensity. Rainfall intensity is classified according to rainfall grade.

2. Flood control department

Rainfall is the depth of the water layer that falls on the ground at a certain point or a certain unit area in a certain period of time, calculated in millimeters. According to the provisions of the Flood Control Manual of the National Defense Office, any 24-hour cumulative rainfall exceeding 50 mm is designated as a rainstorm.

3. Hydrological department

Generally speaking, light rain, moderate rain, heavy rain and rainstorm are generally measured by daily rainfall. Among them, light rain means that the daily rainfall is below 10 mm; Daily rainfall in moderate rain 10~24.9 mm; The rainstorm rainfall is 25~49.9 mm; The rainstorm rainfall is 50~99.9 mm; The rainstorm rainfall is 100~250 mm; The rainstorm rainfall is above 250 mm.

Extended data

There are two kinds of instruments for measuring precipitation: rain gauge and rain gauge.

1. The rain gauge is an instrument used to measure the accumulated rainfall over a period of time. The shell is a metal cylinder divided into upper and lower parts. The upper section is a water funnel with a diameter of 20 cm. In order to prevent the rain from splashing and keep the area and shape of the bottle mouth, the cylinder mouth is made of hard copper into a blade shape with straight inside and oblique outside. Put a water storage bottle in the lower bucket to collect rainwater.

When measuring, pour rainwater into a special rainfall cup and read the millimeters of precipitation. In the snow season, take out the water storage bottle and replace it with one without a funnel. Snowflakes can be collected directly in the rain tube and watched after the snow melts. You can also weigh the snow and convert it into millimeters according to the area of the mouth.

2. Siphon rain gauge is an instrument that can continuously record precipitation and precipitation time. The upper water funnel has the same shape and size as the rain gauge. When rainwater is introduced into the measuring cylinder through the funnel, the float in the measuring cylinder will float with the rise of the water level, driving the self-recording pen to draw the curve of the water level rise on the self-recording paper. When the water level in the measuring cylinder reaches 10 mm, with the help of siphon, the water is quickly discharged, and the pen tip falls back to zero before recording. The self-recording clock gives the cumulative process of precipitation with time.

Siphon rain gauge is a rainfall recording instrument used by most stations. Its advantage is that the structure and mechanical measurement principle are simple and clear, and observers can know the time, intensity and capacity of natural precipitation at any time. The disadvantage is that it is easy to break down, so we must pay attention to strengthening maintenance to ensure the completeness and correctness of records.

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