How is the XX millimeters of rainfall in a certain place often mentioned in weather forecasts measured? What are the standards?
Precipitation within a certain period of time. The depth of rainwater accumulated without any infiltration, evaporation, or loss during this period is called the precipitation amount of the place during that period. The unit is expressed in millimeters (mm). .
PS. The unit of precipitation is the unit of length. The daily precipitation should be read to 0.2mm, preferably 0.1mm; the total weekly or monthly precipitation should be accurate to at least 1mm. The measurement of daily precipitation is best fixed at certain time periods, such as 8 a.m. to 12 p.m.
Rainfall regulations
[Author: Anonymous Reposted from: Original clicks on this site: 189 Update time: 2005-5-24 Article entry: Hu Wenwei]
When we listen to or watch weather forecast broadcasts, we often hear terms such as "light rain", "moderate rain", and "moderate to heavy rain". This is the level of rainfall. Rainfall refers to the rainwater falling on the ground without evaporation, infiltration and loss, and is determined by the depth of accumulation. Our country stipulates that the unit of depth is millimeters. Rainfall levels are divided into light rain, moderate rain, heavy rain, heavy rain, heavy rain and extremely heavy rain based on the amount of rainfall within 24 hours. Light rain: The rainfall is within ten millimeters, and the raindrops are clear and distinguishable. They fall on the roof tiles and hard ground without splashing, and the sound of rain is gentle and pattering. It usually takes two minutes to completely wet the stone slabs and roof tiles, and the puddles form quickly. slow. Moderate rain: The rainfall is between 10 and 25 millimeters. The rustling sound of rain can be heard. The rain falls in lines. The raindrops are difficult to distinguish. There is a slight splash when it falls on the roof holes and hard ground, and puddles form quickly. Heavy rain: The rainfall is between 25 and 50 millimeters. When it rains heavily, the rain falls like a downpour and blurs into sheets. The raindrops fall on the roof tiles and hard ground and splash up to several inches. The sound of rain is like drums, and the pools form extreme quick. Heavy rain: Rainfall between 50 and 100 millimeters, causing water accumulation on the roads. A rainfall between 100 millimeters and 200 millimeters is called a heavy rainstorm; a rainfall of more than 200 millimeters is called a heavy rainstorm, and low-lying areas will be flooded. Showers: refers to bursts of precipitation, with larger raindrops, falling and stopping, and rapid changes in intensity. When it rains, the sky is dark, sometimes it suddenly opens up, revealing a sunny sky, and sometimes it is accompanied by thunder.
The China Meteorological Administration stipulates that the rainfall within 24 hours is called daily rainfall. Any daily rainfall below 10 mm is called light rain, 10.0 to 24.9 mm is called moderate rain, and 25.0 to 49.9 mm is called heavy rain. Heavy rains range from 50.0 to 99.9 millimeters, heavy rainstorms range from 100.0 to 250.0 millimeters, and those exceeding 250.0 millimeters are called extremely heavy rains.
Due to the vast territory of our country, precipitation varies greatly between the east and west, north and south regions. A few areas have other regulations based on the specific conditions of the province and have formulated local standards for heavy rain for local use. For example, in the rainy Guangdong Province, a daily rainfall of more than 80 millimeters is called a heavy rain; in the drier Yan'an region of Shaanxi, a daily rainfall of more than 30 millimeters is called a heavy rain; inland Xinjiang has a dry climate with less precipitation. Rainy days equal to or equal to 10 mm are named "heavy precipitation".
The meteorological department calls rain and snow precipitation, and the amount of precipitation is called precipitation. The unit of precipitation is usually millimeters. 1 mm of precipitation refers to the water depth of 1 mm per unit area. How much does 1 millimeter of precipitation fall on the fields? We know that the area of each mu of land is 666.7 square meters. Therefore, 1 mm of precipitation is equivalent to an increase of 0.667 cubic meters of water per mu of land. Each cubic meter of water is 1,000 kilograms, so 1 millimeter of precipitation is equivalent to pouring about 650 kilograms of water per acre of land. According to measurements, a 5mm rain can saturate dry land by 3cm to 6cm. In the weather forecast issued by the meteorological department, we often hear professional terms such as light rain, moderate rain, and heavy rain. What is the difference between them? Light rain refers to rain that does not exceed 10 mm of precipitation within 24 hours. Light to moderate rain is 5 mm to 18 mm, moderate rain is 10 mm to 25 mm, moderate to heavy rain is 18 mm to 38 mm, and heavy rain is 25 mm to 50 mm, with heavy rain ranging from 38 mm to 75 mm. Rainfall exceeding 50 millimeters in 24 hours is called heavy rain, rain exceeding 100 millimeters is called heavy rain, and rain exceeding 200 millimeters is called extremely heavy rain. In weather forecast parlance, different terms have different meanings. For example, "sporadic light rain" means that the precipitation is very short and the precipitation does not exceed 0.1 mm. "Sometimes light rain" means that the weather is gloomy and sometimes there will be short-term precipitation. "Rainfall" refers to the sudden start and end of precipitation in summer, with heavy rainfall and light rainfall, and the rainfall is relatively large. "Thunderstorm" refers to a rain shower accompanied by thunder and lightning. "Rain in local areas" means precipitation occurs in small areas and is distributed irregularly.