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Rainfall calculation

Measurement method of rainfall:

Rainfall is calculated by rain gauge and rain cup. The rain gauge is a cylindrical open cylinder, and its opening area is 3 14 square centimeter (20 cm in diameter) in China. In order to prevent precipitation from evaporating, the middle and upper parts are leaking, and the water storage bottle is placed at the lower part.

For the convenience of observation, the above caliber is equipped with a special measuring cup. The diameter of the rainfall cup is 4 cm, so the length of precipitation per millimeter on the rainfall cup is 25 mm. In order to record liquid precipitation continuously, the hydrological and meteorological departments often use siphon rain gauge or tipping bucket telemetering rain gauge. Their recording paper not only records the total precipitation, but also can judge the precipitation or precipitation intensity in different periods.

The accuracy is 0.25mm or 0.0 1 inch in terms of the depth of rainwater collected on the airplane. It is sometimes expressed in liters per square meter (1l m-2 =1mm). In meteorological statistics, rainfall can also be called rainfall, that is, the accumulated precipitation in a certain period of time, in which if the precipitation is less than 0. 1 mm, it is regarded as rain trace.

Extended data:

Expression of rainfall:

1, contour line

On a weather map, the connection of points with equal rainfall. It represents the characteristics of rainfall distribution. According to the isohyet condition, the changes of rain area, rainfall gradient and rainstorm area can be analyzed.

2. Rainfall map

The precipitation distribution map of a certain area in a given time period can be divided into years, seasons, months, ten days, days or specific time periods. Weather analysis uses a short period of time, such as a 24-hour rainfall map, to observe the movement and development of weather systems related to precipitation.

Long-term weather forecasting and climate analysis use longer time periods, such as annual, seasonal, monthly or longer rainfall maps to observe long-term weather changes and climate changes. In agrometeorological work, rainfall maps of some crops at certain growth and development stages are mainly used.

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