What is humidity ?
Humidity refers to the amount of water present in the air in the form of water vapour.
The amount of water vapour present in the atmosphere is 4 percent in volume which is very low, yet it plays very important role in the determination of weather and climate of a place.
Humidity of air is directly proportional to the temperature of air.
Because the greater will be temperature of air, the greater will be evaporation of water, so the greater will be humidity( water vapour in air ) of air.
The amount of humidity of air varies spatially and temporally.The amount and intensity of evaporation is more in the oceans.There is maximum evaporation from land between 10 degree North and 10 degree South latitudes, whereas maximum evaporation occurs from the oceans between 10 degree-20 degree latitudes in both the hemispheres.
Humidity Capacity
The moisture retaining of air is called humidity capacity. It refers to the capacity of an air of certain volume at certain temperature to retain maximum amount of moisture content.
Saturated Air and Dew Point:
The air having moisture content equal to its humidity capacity is called saturated air.
The temperature at which the air becomes saturated is called Dew point.
The temperature at which the air becomes saturated is called Dew point.
Higher the temperature, higher the humidity capacity of air, higher the amount of water vapour present in the air.
Humidity is expressed in three forms:
1) Absolute Humidity: The total weight of moisture content per volume of air at a definite temperature is called absolute humidity. It is expressed in gm/ meter cube.
2) Specific Humidity: It refers to the mass of water vapour present in a kilogram of air. It represents the actual quantity of moisture present in the air. It is expressed in gm/kg.
3) Relattive Humidity: Relative humidity is defined as a ratio of the amount of water vapour present in the air having definite volume and temperature(absolute humidity ) to the maximum amount the air can hold (humidity capacity). It is generally expressed in percentage.
relative humidity = absolute humidity/humidity capacity * 100
When the relative humidity is 100%, the process of condensation starts which causes precipitation due to gravity of the earth.
2) Specific Humidity: It refers to the mass of water vapour present in a kilogram of air. It represents the actual quantity of moisture present in the air. It is expressed in gm/kg.
3) Relattive Humidity: Relative humidity is defined as a ratio of the amount of water vapour present in the air having definite volume and temperature(absolute humidity ) to the maximum amount the air can hold (humidity capacity). It is generally expressed in percentage.
relative humidity = absolute humidity/humidity capacity * 100
When the relative humidity is 100%, the process of condensation starts which causes precipitation due to gravity of the earth.
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