What Is Precipitation?
Precipitation is any product of vapour condensation in atmospheric water clouds in various forms, which comes to the surface of the earth under the gravitational pull from the clouds. The main forms of rainfall include drizzle, rain, sleet, snow, ice pellets, graupel, and hail, etc.
Water vapour in clouds accumulates in larger and larger drops of water. When the water vapour cools. Then rain falls on the earth’s surface in various forms.
Dust or smoke particles in the atmosphere help in the process of condensing water vapour for precipitation. Which collects huge drops of water and makes them big enough to fall on the surface of the earth.
Precipitation always falls to the earth as freshwater, even if that water has evaporated from the ocean. However, the effects of pollutants in the atmosphere can contaminate water droplets before precipitation occurs on Earth.
The resulting contaminated rain is called acid rain. Acid rain is not harmful to humans, but it does make the water in lakes and streams more acidic, which has a detrimental effect on plants and animals etc., in aquatic ecosystems, which cannot adapt to acidic water.
Precipitation falls in the form of rainfall in most parts of India. While in an area like the Himalayas.
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Type of Precipitation
- Orographic Precipitation
- Cyclonic Precipitation
- Convective Precipitation
- Precipitation Due to Turbulent Ascent
1. Orographic Precipitation
- Aerographic precipitation is caused by mountain-like obstructions in the passage of moist air. Obstacles like some natural topographic mountains cause rain, which rises above the humid wind due to a mountain-like obstruction. Therefore, the humid air temperature decreases, and condensation occurs. This process results in precipitation.
- A large amount of rain from which humid winds come. That side increases precipitation in greater quantities. This causes very little rainfall on the opposite side of the barrier.
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2. Cyclonic Precipitation
- Cyclonic rainfall is caused by a difference in humid air pressure in the middle. This type of rain causes air from other surrounding areas to move into the low-pressure area.
- The hot and cold air in the air rises due to the motion of the earth. This air cools as it rises, which causes precipitation due to the condensation of air. Such precipitation is called cyclonic Precipitation.
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Cyclonic rainfall is divided into two types
- Frontal Precipitation
- Non-Frontal Precipitation
2.1. Frontal Precipitation:
- In collisions between them due to differences in temperature and density of cold and hot air, condensation of air occurs, which transforms into precipitation. The precipitation that occurs in this way is called Frontal Rainfall.
- If cold air in a cyclone pushes hot air out, it is called a cold front. And in the same way, the hot air in a cyclone pushes out the cold air is called a warm front.
- The precipitation arising from the cold front in a cyclone causes heavy rainfall over small areas. While in cyclones, the precipitation caused by the hot front has a lower intensity. The warm front precipitation is spread over a large area. Thus, the precipitation produced by the cold front in a cyclone proceeds faster than the precipitation produced by the warm front.
2.2. Non-Frontal Precipitation:
- In this type of cyclone, the circulating mass of cold air meets the static warm nature. As a result, cold air pushes hot air upwards. And precipitation is caused by the condensation of hot, humid air. This type of precipitation is called non-frontal precipitation.
3. Convective Precipitation
- Convective rainfall usually occurs in tropical regions in warmer climates. In the equatorial regions, direct sunlight falls on the surface of the water, which increases water evaporation.
- Warm, humid air rises as it is lighter. The warm air cools in cold weather above altitude. This condensation of hot air causes precipitation.
- This type of precipitation is processed according to the convective principle of heat. Hence it is called convective precipitation
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4. Precipitation Due to Turbulent Ascent
- The mass of air rises due to the friction of moist hot air with the surface of the earth.
- This hot, humid air cools as it rises. This results in the precipitation of condensed hot air.
- Winter precipitation in the state of Madras is one such type of precipitation.
Form of Precipitation
The two main forms of precipitation are defined as follows,
1. Liquid Precipitation
- Rainfall type precipitation is prevalent in most parts of India. This type of precipitation occurs in the form of water droplets.
- The size of the water drop in this type of precipitation is between about 0.5 mm and 6 mm.
Rainfall is classified according to its intensity: –
1. Light rain
- The intensity of precipitation in light rainfall is usually 2.5 mm / h.
2. Moderate Rain
- The intensity of this type of precipitation form ranges from 2.5 mm/hr to 7.5 mm/hr.
3. Heavy Rain
- The intensity of this type of precipitation form is more than 7.5 mm/hr.
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2. Frozen Precipitation
- Snowfall is another major form of precipitation. Snowfall is a variety of snow crystals.
- The initial density in the form of ice of the new fresh precipitation is 0.06 to 0.15 g/cu.m. In India, precipitation is a common form of snowfall in the Himalayan region. But Canada, USA, Russia. In cold countries like China, etc., precipitation can be seen in the form of snowfall.
This type of precipitation occurs in the form of irregular pellets of ice larger than 8 mm in size, which comes in the form of precipitation with violent hurricanes.
This type of precipitation occurs in the form of numerous water droplets, which is usually smaller than 0.5 mm in size. The intensity of this type of precipitation is less than 1 neem/hour, which is commonly referred to as drip precipitation.
This type of precipitation occurs in the form of frozen drops of transparent grain, which is formed by precipitation falling in a subfreezing atmosphere.
This type of precipitation occurs in cold climates around 0 C. This precipitation drops freeze to form a layer of ice called glaze or freezing precipitation.
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Measurement of Precipitation
Rainfall Type Precipitation
- Rainfall type precipitation is usually measured in depth. Precipitation is calculated by measuring the depth of precipitation water lying in the earth’s crust. Suppose 1cm of rain falls on a 1km catchment, then the flowering rate of water is 100000 cubic meters.
- The instrument used to measure rainfall is known as a rain gauge. The rain gauge is an open cylinder for collecting and catching rain. Due to the open position of the rain gauge, it collects rain.
The standard-setting conditions of rain gauges for accurate rainfall data storage are as follows.
- The accurate level of the rain gauge is checked and set on a strong surface of open ground.
- The problem of wind effect on the rain gauge is solved. And it is prevented from overflowing against the intensity of the rain.
- Generally for rain gauge should be kept in the open fenced area of 5.5m * 5.5m.
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Two Types of Rain Gauges Are Used to Measure Precipitation
- Non-Recording Rain Gauge
- Recording Rain Gauge
1. Non-Recording Rain Gauge
- Symon’s Rain gauge is a non-recording rain gauge widely used for precipitation in India.
- This type of rain gauge has a circular storage area of 12.7 cm diameter attached to the funnel for storage of precipitation.
- The precipitation reaches the vessel through the funnel. The funnel and vessel are housed in a rain gauge.
- The water collected in the bottle is measured using appropriate measuring tools with an accuracy of 0.1 mm. The depth of precipitation is accurately measured in mm or cm.
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2. Recording Rain Gauges
- This type of ranging gauge provides a permanent automatic record of rainfall. In this type of rain gauge, the measurement of rainfall from the beginning of the record is automatically recorded on graph paper by a mechanical system.
- It makes a graph of accumulated rainfall versus time (mass curve of rainfall). This type of rain gauge is known as an integrated gauge.
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