Precipitation is defined as any liquid or frozen water that occurs in the atmosphere and falls to the Earth's surface. Rain, sleet, and snow are just a few examples. Let's learn about different types of precipitation.

The total volume of water on earth remains the same all thanks to the water cycle. An important mechanism of this complex natural machinery is precipitation in all its forms. And among all the forms the role of rainfall is of supreme importance.

Types of Precipitation

 

There are mainly 3 types of precipitation:

 

Snowfall and Hailstones

 

How are they formed?

Witnessing a snowfall or looking at a landscape filled with big ice crystals or hailstones is an experience one never ceases to be amazed at. Let us understand how these beautiful phenomena occur.

 

1. Snowfall

 

When the precipitation occurs in the form of crystals of ice, it is called snowfall.
� The temperature of the atmosphere decreases with an increase in altitude. If the air mass is full of water vapor at a temperature below the freezing point i.e. dew point, then the moisture from the atmosphere is released in the form of frozen ice crystals.
� Once the water starts freezing in a cloud, the ice crystals in hexagonal shapes start increasing in size.
� Due to melting on the edges, several ice crystals stick together to form snowflakes.
� No two ice crystals are identical in shape. Most of them are variations on a six-sided pattern.
� The diameter of an ice crystal may vary from 1/10th of an mm to about 1mm. Several millions of ice crystals are needed to make 100g of snow.
� Snow is not frozen rain. The term sleet is used for the frozen raindrops and the refrozen melted snow water.

 

2. Hailstones

 

Hailstones consist of pellets or small balls of ice falling on the ground. It is a mass of ice with a layered structure.
� Unlike flakes of snow they are formed due to condensation in the form of ice crystals, hail is formed through freezing drops of water.
� Hailstones usually develop in the cumulonimbus clouds. Small droplets of water are formed in the lower part of the cloud due to condensation. Many of them join together to form large ones.
� The strong rising convection current carries these raindrops to higher levels, which causes freezing and gives rise to small ice pellets. They fall for some distance, slightly melt at the lower levels, and are carried up again.
� This happens several times until the weight of the ice pellets becomes so heavy that they cannot be carried up by the current. Ultimately, these ice pellets fall as hailstones on the Earth.
� The size of the hailstones depends upon the amount of ice they collect during their ascent and descent in the atmosphere by the convection current.
� Hailstorms occur widely in the world, except in the polar regions, the hot deserts, and the equatorial region.
� The occurrence of the hailstones is common during the spring and the early summer in the subtropical and temperate regions.

 

3. Rainfall

 

Rain is one of the most important types of precipitation. We see them coming from clouds but how are clouds formed?

 

Formation of Clouds

 

Clouds are the droplets of water or tiny ice crystals which collect around the dust and other particles present in the atmosphere. Clouds are a product of condensation and are the main bodies responsible for all kinds of precipitation. The water or ice that makeup clouds travel into the sky within the air as water vapor.

 

Do you know how water vapor gets into the air?

 

Water vapor gets into the air mainly by evaporation � some of the liquid water from the ocean, lakes, and rivers turns into water vapor and travels into the air.

 

� When air rises in the atmosphere it gets cooler and is under less pressure.
� When air cools, it�s not able to hold all of the water vapor it once could. Air also can�t hold as much water when air pressure drops. The vapor becomes small water droplets or ice crystals and a cloud is formed.
� It�s easier for water vapor to condense into water droplets when it has a particle to condense upon. These particles, such as dust and pollen, are called condensation nuclei.

Eventually, enough water vapor condenses upon pieces of dust, pollen, or other condensation nuclei to form a cloud. It�s important to note that though all kinds of precipitation occur through clouds, not all kinds of clouds cause precipitation.

 

The water vapor that has condensed into tiny droplets and formed clouds are called cloud droplets. They are well on their way to becoming rain � but it's not there yet. For now, the water droplets are so tiny that the air currents keep them aloft, just as swirling particles of dust can stay in the air.

 

But as those droplets continue to rise, buoyed by rising bodies of warm air, they start becoming heavier. Once these cloud droplets become so large and heavy that the air is not able to hold them in suspension, down they come in the form of raindrops.

 

Rainfall

 

Rain is any liquid that falls from the clouds. Rain is defined as water droplets with a diameter of 0.5 mm or greater. Drizzle is described as a droplet size of less than half a millimeter. Raindrops form when microscopic cloud particles collide and join together to form larger drops.

 

As the process continues, the drops become larger and larger until they are too heavy to be suspended in the air. Gravity drags them down to the ground as a result. Raindrops begin to fall as ice crystals or snow when they are high in the air, but they melt as they travel down the earth through warmer air.

 

Rainfall rates vary from time to time; for example, light rain falls between 0.01 and 0.1 inches per hour, moderate rainfalls between 0.1 and 0.3 inches per hour, and heavy rain falls between 0.3 and 0.5 inches per hour. Rain is the most prevalent component of the water cycle, replenishing the majority of the world's freshwater.

Do you know what are the conditions for the formation of rain?

The following conditions are necessary for rains to occur:

 

1. There should be a sufficient amount of evaporation from the water bodies.
2. There should be a wind to carry the water vapor from one place to another.
3. There should be some way of decreasing the temperatures of the moist air.

 

The diameter of a raindrop is about 6mm and one raindrop contains about 8 million cloud droplets.

 

Types of Precipitation MCQs

 

1. What is the diameter of an ice crystal that forms snow?
(i) 1/50 of mm to 1 mm
(ii) 1/200 of mm to 1/100 mm
(iii) 1 mm to 2 mm
(iv) 1/10 of mm to 1 mm

 

2. Hailstorms occur in which of these regions?
(i) Polar regions
(ii) Hot deserts
(iii) Equatorial regions
(iv) Temperate regions

 

3. Which of these factors causes a decrease in air temperature?
(i) Decrease in pressure
(ii) Increase in pressure
(iii) Decrease in altitude
(iv) Increase in altitude

 

4. In which season is the occurrence of hailstorm common?
(i) Winter
(ii) Autumn
(ii) Spring
(iv) Summer

 

5. Which of these is formed due to the condensation of ice crystals?
(i) Hailstones
(ii) Sleet
(ii) Rain
(iv) Snow

Read More: What is Precipitation: Process, Condition Necessary, and Distribution - Class 9