What Is Precipitation?
Precipitation Is one of the essential processes in the global water cycle. Precipitation is the falling of liquids or solids from the atmosphere onto the earth’s surface, such as Rainfall, Snowfall, etc.
In comparison, other processes like evaporation and condensation contribute to the precipitation and a never-ending water cycle.
How Precipitation Occurs
Precipitation occurs when the atmosphere has adequate moisture, which gets condensed in the presence of sufficient nuclei such as salt particles, particles of combustions, etc.
Weather conditions play a vital role in the condensation process. If the condition is not favorable, it leads water vapor to condense into tiny water droplets. These small water droplets are usually less than 0.1mm in diameter size.
The clouds in the atmosphere get carried by the wind when two clouds get combined. This results in heavier water droplets or cloud drops that can no longer float in the atmosphere, resulting in falling to the earth’s surface, which is called precipitation.
The precipitation can be in many forms like snow, hail, sleet, drizzle, or rain. As we know, the process of cooling air mass happens only when the air masses rise. It is to a higher altitude.
So, there are three different precipitation methods to lift the air masses to a higher altitude, which are explained below in detail.
Different Forms Of Precipitation
Precipitation can occur in 6 different forms, such as
Rain is a common type of precipitation that falls onto the earth’s surface in the form of water droplets. These droplets are larger than 0.5mm.
Usually, the larger water droplets break into smaller droplets when it falls on the earth’s surface. The maximum size of water droplets is 6mm.
Rainfall generally occurs when water vapor gets condensed into bigger droplets; when these water droplets get heavy, they fall on the earth’s surface in the form of rain.
Drizzle is a very light type of rain. But unlike fog droplets, drizzle droplets fall on the earth’s surface. In this, the water droplets are fine and very close to each other drizzle tends to flow with the air currents.
Drizzle water droplets size is less when compared to rainwater droplets; its size comes less than 0.5mm with an intensity of 1mm/hr.
Snow precipitates in the form of ice crystals which as an average density of 0.1g/cc. Snow can be seen in colder climates and higher altitudes. But if the temperature is above freezing, then these ice crystals can partially melt.
Due to relatively warm temperatures, these partially melted crystals are evaporated immediately. This evaporation helps cool the ice crystals and makes them reach the earth’s surface as snow.
The glaze is an ice coating usually formed when rain or drizzle comes in direct contact with the clod earth’s surface at 0 degrees Celsius.
Even though the droplets freeze instantly, they still have sufficient time to spread over into a layer.
The ice coating layer is denser and harder and appears more transparent. The glaze is also known as Black Ice.
Sleet is formed into frozen raindrops when the rainfall passes through the air at sub-freezing temperatures. These are also known as ice pellets.
Sleet usually appears in a small and semi-transparent ball of ice. Which look like hailstones, but these come in a small size while hailstone comes larger in size.
Hailstones are big and irregular shape ice balls that fall due to thunderstorms. Hailstones are larger than 8mm. Hailstone’s precipitate in the form of a solid. These are mostly made of water ice, which is about 0.2” to 6” in dia.
Types Of Precipitation
As we know, cooling air mass happens only when the air masses rise to a higher altitude. So, there are mainly three different types of precipitation methods to lift the air masses to a higher altitude. Which as follows:
- Cyclonic Precipitation
- Convective Precipitation
- Orographic Precipitation
1. Cyclonic Precipitation
Cyclonic precipitation occurs when the mass of air rises due to low pressure or due to pressure differences.
These are further classified into two types
- Frontal Precipitation
- Non- frontal Precipitation
i) Frontal Precipitation
Frontal precipitation is caused due to expansion of air near which is near to the frontal surface. It is also known as Hot moist air mass boundary.
ii) Non-Frontal Precipitation
Non-Frontal precipitation is formed due to the movement of a cloud moist air mass boundary.
2. Convective Precipitation
These types of Precipitations occur when convection or transmission of warm moist air happens. Convective precipitation occurs when hot air rises, gets cooled and precipitates back to the earth’s surface.
These types of precipitations are showery and occur in varying intensities. Convective precipitation can be seen in a small range of areas like less than 10km in dia.
3. Orographic Precipitation
Orographic precipitation occurs when the air masses get struck against large mountains. That leads to raising the air masses up, resulting in condensation and precipitation.
Orographic precipitation is more on the windward side of mountains when compared to the downward side of the mountain or barrier.
Different types of rainfall based on their precipitation intensity are given in the below table.
Precipitations are generally measured using a rain gauge, but nowadays, precipitation intensity is more easily measured using remote sensing techniques like weather radar.
|Type of Rainfall||Rainfall Intensity (mm/h)|
|Moderate||2.5 to 7.5|
Snowfall intensity are generally classified based on the visibility
|Type of Snowfall||Snowfall Intensity||Snowfall Visibility|
|Light||> 0.62 mi||Over 1km|
|Moderate||0.31 mi to 0.62 mi||Between 0.5Km to 1km|
|Heavy||< 0.31 mi||Below 0.5km|
Different Precipitation Sizes
The precipitation from the atmosphere happens in various forms of various sizes, some of these are mentioned below
|Precipitation Form||Precipitation Size||Precipitation State|
|Rain||0.5 to 5mm||Liquid|
|Snow||1mm to 2cm||Solid|
|Glaze||1mm to 2cm||Solid layer|
|Sleet||0.5 to 5mm||Solid|
|Hail||5mm to 10cm+||Solid|
Also Read –