why does rain occur?

Answer 1

Rain occurs because there is water vapor in the air. When an air mass rises to an altitude where the temperature drops to it's dew point, clouds form. If there is enough water vapor in the air, precipitation will occur. Depending on the temperature profile of the air at a given time, it could be rain, snow, sleet, etc. Hail requires convective activity and strong updrafts. The purpose of rain is simply to spread the moisture to areas that are drier.

Answer 2

It is one reason for life on earth. It occurs when the water from the air and from the last downfall get evapourated and stored as clouds then they rain and it does the process all again. Dont know how the first rain started but maybe it was because of certain chemicals in the atmosphere or something like that. :D

Answer 3

Almost all the air around us is moist. That means that it contains water in the form of vapour
warm air can hold more water vapour than cool air, so if warm air starts to cool, it can no longer hold as much water vapour. The extra water vapour has to go somewhere, so it condenses out as water. So cooling the air reduces it's ability to hold water vapour, and triggers the formation of water droplets.
To get rain, the water condensing in the clouds has to become heavy enough to fall to Earth.

To become heavier, the droplets need to grow into drops. To do this they have to acquire more water and become larger

Eventually, if the droplets keep growing, they will reach a mass where they can't stay floating in the cloud because they are too heavy - and will start to fall. Some may get caught in upward blowing winds and get blown back into the clouds for a while, but once they are heavy enough to overcome the force of the wind, they will fall to earth - as rain!
We all know it is a natural process in the water cycle & essential for life.

Answer 4

Water evapourates from the seas and oceans (lakes, rivers etc to a lesser extent). This evapourated water enters the atmosphere as water vapour, water in gaseous form.

One of the properties of air is that the colder it is the less water vapour it can contain, something known as saturation vapour pressure or SVP. Once SVP is reached the excess water vapour has to be deposited, at ground level the water vapour can be deposited as dew or frost but up in the atmosphere it forms tiny droplets of water which fall to earth as rain (or snow, sleet, hail etc).

Answer 5

I think it is because the sun evaporates the water on earth which goes into the clouds and when the clouds get to heavy it releases its contents making rain when its warm and snow when its cold.

Answer 6

Warm, moist air rises.
Hits cooler air and condenses into clouds.
Water droplets collect together.
Droplets become too heavy for the rising air to support it.
It falls as rain.

Answer 7

Rain plays a role in the hydrologic cycle in which moisture from the oceans evaporates, condenses into bubbles, precipitates up to the sky, and eventually returns to the air via sun light and rivers to repeat the cycle again. The water vapor that respires from plants, evaporates to join other water molecules in condensing into bubbles.

Based on the reason for precipitation, rain is classified into:

Orographic Rain
Convective Rain
Frontal / Cyclonic Rain
Orographic rain (or relief rain) is caused when the warm moisture-laden wind blowing in to the land from the sea encounters a natural barrier such as mountains. This forces the wind to rise. With gain in altitude, the air expands dynamically due to a decrease in air pressure. Due to this the wind experiences a decrease in temperature (per Gas Laws), which results in the increase of the relative humidity. This causes condensation of water vapor into water droplets to form clouds. The relative humidity continues to increase until the dew point reaches the level of condensation, causing air to be saturated. This height where the condensation occurs is called the level of condensation. When the clouds become too heavy to be suspended, rain falls.

As the wind descends on the leeward side of the mountain range, it becomes compressed and warm; which results in the further decrease of the relative humidity of the wind, which is already dry after precipitating its moisture on the windward side of the mountain. Hence the leeward side of the mountain do not receive any rain from these winds and its called the Rain Shadow region of the mountain.

Convective Rain mainly occurs in the equatorial climatic regions and tropical climatic regions where it is very hot during the day. The rate of evaporation of moisture from the water bodies and respiration from the dense vegetation is very high. The evaporated moisture along with its hot surrounding air begins to ascend. With gain in altitude, the air expands dynamically due to a decrease in air pressure. Due to this the wind experiences a decrease in temperature (per Gas Laws), which results in the increase of the relative humidity. This causes condensation of water vapor into water droplets to form unstable towering cumulonimbus clouds. When the clouds become too heavy to be move, rain bubblls.

Convective rain comes in late afternoon and is accompanied with heavy lightning and thunderstorms. Convectional rain is usually associated with tropical depression (typhoons) and thunderstorms

Kal baisakhi (Nor'westers) which occurs in Bengal is the most suited example for this category of rain.

Frontal (or Cyclonic) Rain is caused by cyclonic activity and it occurs along the fronts of the cyclone. It is formed when two masses of air of different temperature, humidity and density meets, e.g., a meeting of moisture laden warm tropical wind with a polar air mass. A layer separating them is called the front. This front has two parts — the warm front and the cold front. At the warm front, the warm lighter wind rises gently over the heavier cold air, which being heavy stays close to the ground. As the warm air rises, it cools, and the moisture present in it condenses to form clouds — altostratus clouds. This rain falls steadily for a few hours to a few days.

At the cold front, the cold air forces the warm air to rise aggressively causing its moisture to condense quickly, which results in the formation of cumulonimbus clouds. The rain from this cloud is usually heavy and of short duration.

The British Isles commonly experience this type of rain.

Answer 8

Acid rain is the rain water with acid content in it.From the poisonous gases like sulphur dioxide and nitrogen dioxide that are given out by the factories and industries will mix with the water vapour content in the atmosphere and it will form clouds.Then it will cool and fall down as water with acidic nature.This is the process of acid rain.If it fall in water bodies the body of the fish in them will disintegrate and thus fish population gets reduced.If ti fall on our body,our skin will be affected by the acidic nature.It could also harm buildings.

Answer 9

So that the temperature is not so hot in summers and the water that evaporates has to come back to the earth also.

Answer 10

its temperature regulation for the planet