A Short Note On Precipitation

What is Precipitation?

Precipitation is defined as the return of solid or liquid particles on the earth’s surface in any form. Precipitation occurs when water in either solid or liquid form falls on the earth. The solid and liquid particles may be called rain, snow, drizzle, snow pellets, crystals, hail storms.

 How Does Precipitation Occur?

The Hydrological cycle that exists on earth and maintains the continuous exchange of water between the earth and its atmosphere consists of three processes- evaporation, condensation, and precipitation. Water present in different water bodies on the earth’s surface evaporates and is carried by the air currents condenses to form clouds, and finally returns to the earth’s surface in the form of precipitation. It is evident to note here that the average amount of water vapor in the air is almost equal to a 1-inch layer of water covering the whole earth’s surface. 

What Are The Different Forms of Precipitation?

Rain

The water droplets of size more than 0.02 inches are considered rain. The smaller droplets are also considered rain but they should be widely separated. Rainfall occurs when two or more water droplets merge and form a single water droplet. The shape of the droplet is spherical and their sizes vary from 0.1 to 0.9 millimeters. 

There is an exception to rain which is called acid rain. Acid rain occurs due to the mixing of various atmospheric pollutants with the raindrops. Although acid rain is not harmful to the human skin, it is incredibly detrimental to the environment. 

Drizzle

Drizzle is a variation from the rain in the sense that the water droplets are slightly smaller than those of rain. Drizzle occurs when the upward air currents in the clouds are not strong enough to let the clouds produce rain drips of bigger sizes. The credit for drizzling goes to the low-level clouds also called stratiform clouds. Drizzle usually occurs at the colder places where the temperatures are below 10 degrees Fahrenheit. 

Glaze/ Freezing Rain 

The glaze is a kind of precipitation that usually occurs when the water droplets come in contact with the cold surfaces. As this process occurs, the water droplets freeze as soon as they hit the colder surface and form a coating of ice on the surface. As the process continues, the water droplets form a thin and compact layer of ice on the surface. Glazes usually occur after an ice storm and it causes too much destruction on the cables, trees, etc.

Sun Shower

The sun shower as the name suggests is a strange process of precipitation in which there are no clouds but there is rain in the presence of the sun. It occurs when there is rainfall in a different area and the raindrops are brought by the winds to the area where the sun is shining. Also, sun showers also occur at places when a small rain cloud passes over the area of no rain clouds. After the sun shower, usually rainbows are visible due to the lower angle of the Sun.

Ice Pellets/ Sheets

These are small balls of ice falling over the earth’s surface. Usually, these are not larger like hail storms but at times they can be larger in size too. They are formed from rain passing over the air at lower temperatures. Their physical structure is similar to hailstorms in the sense that they are spherical in shape and translucent in nature. They reproduce a sound when they hit the ground. 

Small hail/ snow pellets

Also referred to as “graupel”, snow pellets occur when low-temperature water droplets freeze over the falling snowflakes. These low-temperature water droplets gather and form conical-shaped or rounded ice particles. Due to their structure, snow pellets are easily destructible and tend to break upon hitting the earth’s surface. 

Snow grains

These are small-scaled and elongated snow particles with a diameter being around 1 millimeter. Snow grains usually fall in small amounts and do not break when they hit the earth’s surface,

Hail 

When lower temperature water droplets come in contact with the dust particles present in the atmosphere, hails are formed. The sizes of hails can vary from 5 millimeters to 2-3 centimeters. They are the associates of thunderstorms. 

Diamond Dust

These are formed at places where the temperature ranges are around -40 degrees celsius. Usually, diamond dust falls when there are clear skies and are ground-level clouds made of ice crystals. 

Types of Precipitation 

Cyclonic precipitation

A cyclone is formed at a region of lower pressure and cyclonic precipitation occurs due to the lifting of the moist air mass due to the difference in pressures. These are of two types- 

Frontal precipitation- occurs when hot air expands near the frontal surface

Non-frontal precipitation – occurs due to the movement of a cold moist air mass.

Convective precipitation

Convectional rain is formed from warm moist air that rises over the ground, condenses, and precipitates.

Orographic precipitation

Orographic rain occurs when warm moist air rises quite high over mountain ranges and while doing so, it gets cooled and from orographic clouds. These orographic clouds precipitate later on over the mountains.

Conclusion

Precipitation is a phenomenon that is integral to the survival of various life forms. The amount of precipitation varies widely and is one of the greatest blessings for the environment.