Precipitation refers to the phenomenon that the water vapor in the air condenses and falls to the surface. It includes two parts. One is the condensation of water vapor in the atmosphere directly on the ground or the surface of the ground and low altitude, such as frost, dew, fog and mist. It is horizontal precipitation; the other part is water vapor condensate that landed on the ground from the air, such as rain, snow, hail, and rain, and is also called vertical precipitation. But pure frost, dew, fog, and mist are not treated as precipitation. In China, the National Meteorological Administration's ground observation regulations stipulate that precipitation refers only to vertical precipitation, and horizontal precipitation is not treated as precipitation. Precipitation does not necessarily have precipitation, and only effective precipitation has precipitation. Within a day, precipitation above 50 mm is heavy rain (heavy rain), above 25 mm is heavy rain, 10-25 mm is moderate rain, below 10 mm is light rain, above 75 mm is heavy rain (heavy rain), and above 200 mm is extreme rain.
During the rise of water vapor, as the surrounding air pressure gradually decreases,
The main processes thatproduceprecipitationare:
There are three conditions for the formation of precipitation:
One is to have sufficient
More year round
Atmospheric precipitation is the surface
The spatial distribution of precipitation, which is usually expressed by contour maps of precipitation, which can also be calculated from the map.
Precipitation is measured by the layer of water formed on an impermeable surface, the unit is
Artificial precipitation, also called artificial rainfall, is based on the physical characteristics of different clouds, and chooses the right time to use planes and rockets to disperse dry ice, silver iodide, salt powder and other catalysts into the clouds to promote cloud precipitation or increase precipitation. Artificial rain enhancement is often divided into Jinyun catalyst and cold cloud catalyst. In order to get precipitation from clouds (clouds with a temperature higher than 0 ° C), it is necessary to make the large cloud droplets with a radius greater than 0.04 mm in the cloud have sufficient number density to allow them to quickly collide with small cloud droplets and grow to a radius of more than 1.0 mm. Raindrops form precipitation, so in those clouds with a large number of droplets that are not dense enough to form rainfall, airborne cannonballs and other methods are used to spread hygroscopic particles such as salt powder and urea to cause the formation of many large cloud droplets. Form or increase precipitation. For cold cloud precipitation, the number of ice crystals in the upper part of the cold cloud must exceed 1 per liter. For those cold clouds with insufficient ice crystal number density, the use of airplanes and other catalysts such as dry ice and silver iodide can generate a large number of ice crystals, which can cause or Increase precipitation. In order to clarify the effect of artificial catalysts and the amount of artificial rainfall increase, tests are often performed. Due to the complexity of cloud and precipitation processes, the methods and measures of artificial precipitation and precipitation inspection are still incomplete, and further research is needed.
