What kind of rain is considered heavy rain? Why are 50 and 100 mm important rainfall scale nodes?

Review expert: Ye Haiying, deputy director of the New Media Center of the Meteorological Publicity and Science Popularization Center of the China Meteorological Administration (China Meteorological News Agency)

Beijing is about to enter the flood season, and rainstorms are becoming more frequent. Last Saturday, Beijing welcomed rainy weather. According to Beijing Meteorological Bureau, the average precipitation in Beijing was 18.5 mm, and the average precipitation in the urban area was 22.1 mm. The maximum precipitation occurred in Luozhuang Village, Tongzhou, at 43.3 mm.

The precipitation distribution map of Beijing from 02:00 to 15:00 on May 25 Source: Beijing Meteorological Bureau

According to the national heavy rainfall forecast map from 08:00 on the 27th to 08:00 on the 28th issued by the Central Meteorological Observatory, the rainfall was mainly concentrated in the eastern part of Jiangnan, South China and the Sichuan Basin, with the central value of precipitation reaching 120 mm at one point.

National precipitation forecast map source: Central Meteorological Observatory

Rainy weather has arrived. Understanding and correctly interpreting rainstorm warning signals has become an essential skill in our lives. Under what circumstances will a rainstorm warning signal be issued? What is the difference between warning signals of different colors? Once a warning signal is issued, how should we respond? Next, let's learn about it together!

About the rainstorm warning signal

01

What kind of rain is considered heavy rain?

In meteorology, rainfall is used as the judgment standard. When the cumulative rainfall in a certain area reaches more than 16 mm in 1 hour, more than 30 mm in 12 hours, or more than 50 mm in 24 hours, it can be called heavy rain .

When the above standards are met, it can be further divided into three levels according to the amount of rainfall: heavy rain, torrential rain and extremely heavy rain .

02

What is a rainstorm warning signal?

The heavy rain warning signal is one of the meteorological disaster warning signals . It is a warning signal made by the meteorological department through meteorological monitoring before the arrival of heavy rain.

The meteorological authority of the State Council is responsible for issuing, canceling and disseminating national rainstorm warning signals, such as the blue warning and yellow warning for rainstorms issued by the Central Meteorological Observatory. Local meteorological authorities at all levels are responsible for issuing, canceling and disseminating warning signals within their administrative regions, such as the blue warning signal for lightning issued by the Beijing Meteorological Bureau.

03

What is the relationship between warning signal color and level?

In daily life, we can always see the meteorological department issuing warning signals of different colors. Why are there so many warning signals of different colors? What do the different colors mean?

Meteorological disaster warning signal source: CCTV News

The level of warning signals is divided into four levels according to the degree of harm, urgency and development trend that may be caused by meteorological disasters: Level IV (general), Level III (relatively serious), Level II (serious), and Level I (particularly serious), represented by blue , yellow , orange and red respectively, and labeled in Chinese and English.

04

Are heavy rain warning signals issued randomly?

With the arrival of the rainy season, rainfall will become a common occurrence and heavy rain warnings will also appear. What are the standards for issuing heavy rain warning signals?

Schematic diagram of rainstorm warning signal Source: Sogou

Heavy rain warning signals are divided into four levels, represented by blue , yellow , orange and red .

Blue rainstorm warning

The rainfall will reach more than 50 mm within 12 hours, or has reached more than 50 mm and the rainfall is likely to continue.

Yellow rainstorm warning

The rainfall will reach more than 50 mm within 6 hours, or has reached more than 50 mm and the rainfall is likely to continue.

Heavy rain orange warning

The rainfall will reach more than 50 mm within 3 hours, or has reached more than 50 mm and the rainfall is likely to continue.

Heavy rain red alert

The rainfall will reach more than 100 mm within 3 hours, or has reached more than 100 mm and the rainfall is likely to continue.

It seems that 50 mm and 100 mm are important scale nodes in rainfall. How can we quickly judge the amount of precipitation?

How much is 50mm? Source: CCTV

50 mm is approximately the width of three fingers from the index finger to the ring finger of an average adult.

How much is 100 mm? Source: CCTV

A water depth of 100 mm is above the ankles of an adult.

How to respond to the heavy rain warning signal?

After the heavy rain warning signal is issued

What should we do?

What can be done

1. Pay attention to weather forecasts and warning information, try to reduce going out, take the initiative to avoid risks, and properly place items that are easy to fall on the balcony.

2. When walking outdoors, avoid manhole covers, billboards, and stay away from temporary structures, dilapidated walls, large trees on the roadside, etc.

3. When driving outside, pay attention to controlling the speed and keep a proper distance between vehicles. If you encounter a traffic accident or vehicle breakdown, quickly pull over and evacuate and call the police to prevent a secondary accident.

4. Do not visit, camp or sleep outdoors in mountain valleys, tidal flats, rivers, floodways and other areas.

5. Suspend large outdoor gatherings and high-altitude and outdoor operations.

6. Be alert and guard against secondary disasters such as mountain torrents, mud and rock flow, landslides, urban waterlogging, etc. that may be caused by heavy rainfall.

The danger is not over after a rainstorm. The rainy season has arrived in the south and is getting closer to the north. During and after the rain, live upstairs instead of downstairs, live in the front house instead of the back house, do not dig hillsides, do not clear ditches, be alert to abnormal sounds coming from a distance, and spend the rainy season smoothly.