Cyclonic precipitation refers to the type of precipitation that occurs when moist air rises and cools within the cyclone or low-pressure system. The air cools as it rises, causing water vapor to condense and form clouds. These clouds can produce precipitation in the form of rain or snow, depending on the temperature and altitude of the cloud formation.
Cyclonic precipitation is a common phenomenon in many parts of the world and can result in significant rainfall and flooding. Understanding the mechanisms behind cyclonic precipitation is important for predicting and mitigating the impacts of extreme weather events.
There are 3 types of precipitation that occur on earth Cyclonic Precipitation, Convective Precipitation, and Orographic Precipitation.
- Cyclonic Precipitation
- Convective Precipitation
- Orographic Precipitation
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Cyclonic Precipitation
Cyclonic rainfall occurs when air mass rises due to pressure differences. When there is the formation of a low-pressure area, air from the other surrounding spaces flows to less less-pressure zone.
It is a phenomenon that forces warm and colder air to meet. As warm air is lighter in comparison to colder ones it rises above the colder air. Then the warmer air starts cooling beyond saturation point which results in heavy rain. Such rainfall is called Cyclonic Rainfall.
Cyclonic Precipitation itself is categorized into two types,
- Frontal Rainfall
- Non-Frontal Rainfall
Frontal and non-frontal precipitation are described below:
Frontal Precipitation
The collision of two different air masses, due to differences in temperature and densities, results in condensation and precipitation at the contact surface.
This contact surface is named as Frontal Zone, whereas the precipitation occurring in that zone is called Frontal Rainfall.
If cold air drives out warm air then the front is called a Cold Front and if the Warm nature masses of air overlap the superior cold air mass, it can be known as a warm Front. Similarly Stationary Front is the result of both air masses are moving toward an area of low pressure in a simultaneous way.
Intense Precipitation is the result of the Cold Front spread over a shorter area as compared to a warm nature front which covers a larger area but has a low intensity of the precipitation.
Non Frontal Precipitation
This phenomenon occurs when the moving mass of cold air meets the stationary warm nature of air mass. As a result of which the lighter warm air rises up and reaches the saturation point.
The saturation point of lighter warm air causes precipitation known as Non-Frontal Precipitation. It is a type of Cyclonic Precipitation. This process differs from Frontal Precipitation in some sense hence categorized as a different type of Cyclonic Precipitation.
Convective Rainfall
Convective Precipitation or Convectional Rainfall generally occurs in equatorial areas. The surface areas in these zones get heated frequently and constantly because of the sun’s heat.
Which in turn the air near the surface gets hated and spreads. Heating also makes the air lighter hence it tends to rise up. The air starts cooling as it moves up and reaches its saturation limit, resulting in precipitation.
This precipitation is called Conventive Precipitation, which occurs in the tropics that too on a hot day. Rising vertical velocities of air currents are dangerous to aircraft. Its intensity ranges from light showers to cloud bursts.
Orographic Precipitation
Orographic Precipitation occurs when the moist mass of air, strikes natural barriers of the topography area. These barriers are like mountains, hills, etc which cause the air to rise up, condense, and then precipitate. Hence mountains are the sites of higher precipitation than plain lands.
The precipitation is concentrated on the side of the windward, the side where striking occurs. Whereas, the side of the leeward gets a very little amount of rain, which results in the formation of a rain shadow region.
Forms of Precipitation
The following are the Precipitation forms,
- Rain
- Snow
- Drizzle
- Glaze
- Sleet
- Hail
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1. Rainfall
Rain is the major source of precipitation in the region of India. Rainfall is the term used for precipitation in form of the water drops.
In rainfall, the water drop size is about 0.5mm and less than 6mm. The Range of the Drop is Between 0.5mm to 6mm.
The Rainfall is classified based on its intensity:-
I. Light rain
The intensity of the rain was traced to 2.5mm/hr. then is called the Light Rain.
II. Moderate Rain
The intensity is between 2.5mm/hr. to 7.5mm/hr. is called Moderate Rain.
III. Heavy Rain
The intensity is greater than 7.5mm/hr. is called Heavy Rain.
2. Snowfall
Snow is the second major source of precipitation. Snow generally consists of ice crystals. Ice crystals are combined together and form flakes.
The density of the Fresh Snow is varying between 0.06-0.15 gm/Cubic cm. The average density of the snow is generally considered to be 0.1gm/Cubic cm.
In India, the Himalayan is the only region where snow is fall.
3. Drizzle
Numbers of water droplets fall in the form of fine sprinkles known as Drizzle. The Size of the droplets is less than 0.5mm and the intensity of the Droplets is less than 1mm/hr.
4. Glaze
If the temperature of the ground is around 0* Celsius and the rain or the drizzle are come to contact to the ground the water droplets are frozen and coated with ice is known as Glaze.
It is also known as Freezing Rain.
5. Sleet
The Rainfall passes through the sub-freezing temperature of the atmosphere the raindrops freeze in form of transparent grains is known as sleet.
6. Hail
When the Snow is falling in the form of irregular pellets and a lump of ice is known as Hail. The size of the Hail is more than 8mm. Generally in Violent thunderstorms, Hails occur.
Measurement of Precipitation
Rainfall
Rainfall is generally measured in the form of depth. Rainfall is calculated in the form of how much water depth falls on the earth’s area.
Thus if the 1cm of rainfall falls over the catchment of 1sq.km it represents that the volume of water is 100000 cubic meters.
The Instrument which is used to collect and measure the Rainfall is Known as the Rain Gauge. The rain gauge is consisted of one open cylinder vessel to catch the rainfall in it. The exposure condition of the rain gauge affects the rainfall catch.
For Accurate Data collection the rain gauge is set in a standard-setting position in the following manner:-
- The rain gauge is set on Level and open ground and perfect horizontal position.
- A rain gauge is Put as near the ground to reduce the wind effect but also prevent splashing and flooding.
- Rain gauge is put in the open fenced area of 5.5m * 5.5m.
There are two types of Raines
- Non-recording Rain gauge
- Recording Rain gauge
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1. Non-recording Rain gauge
Symon’s Rain gauge is the extensively used Non-recording Rain gauge in India. This type of rain gauge has a 12.7cm diameter to collect the rainfall which is connected with a funnel.
The rim of this collector is set in a horizontal plane at a height of 30.5cm above the ground. Rainfall is caught through the funnel in receiving vessel. Both the funnel and vessel are mounted in a metallic container.
The water is collecting in the vessel is measured with a suitable graduated measuring glass with high accuracy of 0.1mm. The rainfall is measured at 8:30 am (IST) and recorded as everyday rainfall.
The capacity of Symon’s rain gauge is 10cm only so in heavy rainfall conditions rainfall is measured more frequently and entered.
2. Recording Rain Gauges
Recording rain gauges are used for continuous plots of the rainfall against time with valuable data of intensity and duration of rainfall.
Types of Recording Rain Gauge
- Tipping Bucket type
- Weighing Bucket type
- Natural Syphon type
- Telemetering Rain gauge
- Radar Measurement of Rainfall
1. Tipping Bucket Type
A tipping Bucket type of rain gauge is adopted for use by the US Weather Bureau. The size of the rain gauge is 30.5cm. The rainfall is caught in the funnel and falls on one of the pairs of small buckets.
This pair of bucket is set so systematically that when one bucket of 0.25mm of rainfall collects it tip down and another one is brought into position.
After tipping the bucket the water is collected in a storage can. The electrically driven pen traces a record on a Clockwork-driven chart with each tipping.
The water which is stored in the can is also measured at regular intervals to get total rainfall and also for the check. The tipping bucket gives the data which is in form of the intensity of rainfall.
2. Weighing Bucket Type
In the weighing Bucket type of rain gauge the rainfall was caught from the funnel and it empty in the bucket which was mounted on a weighing scale.
The weighing bucket is recorded on a clock-work-driven chart. Weighing bucket-type rain gauge gives the mass curve of rainfall. (Intensity and Duration).
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