When water evaporates it forms the gaseous water vapour. The amount of water vapour in the air at any one time is known as its humidity. AS more and more water vapour saturates the air, humidity increases, eventually resulting in rain, fog or mist, depending on the heat and temperature of the place.

Humidity is the amount of moisture or water vapour or water molecules present in the atmospheric gas. The more water in the vapour, the higher the humidity. Humidity arises from water evaporating from places like lakes and oceans. Warm water evaporates quickly. That’s why; you may find the most humid regions near to warm water bodies in places like the Red Sea, the Persian Gulf, and Miami.

Types of Humidity:

  1. Relative humidity: A meteorologist uses the term ‘relative humidity’. The relative humidity is a comparison of the amount of moisture present in the air to the amount of moisture air can hold. The amount of moisture the atmosphere can hold totally depends on the temperature.
  1. Specific humidity: We define specific humidity as the mass of water vapour present in a given unit mass of moist air.

Specific humidity is equal to the ratio of water vapour mass and the air parcel’s total (including dry) air mass.

Specific humidity is also known as the humidity ratio. It does not change with the expansion or compression of an air parcel.

We usually express specific heat as grams of vapour per kg of air, or in air conditioning as grains per pound.

The specific humidity has great usage in meteorology.

3. Absolute humidity: We define the absolute humidity in the two following sentences:

Absolute humidity is equal to the mass of water vapour per unit of volume of air, i.e., grams of water/cm3 of air. The formula for the absolute humidity is given by:

             Absolute humidity = Mass of water/volume in cm3

Absolute humidity does not take temperature into consideration.

Credit: Vedantu

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