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What is the relationship between temperature of the air and dew point temperature?

  • A

    If the pressure is kept constant, with a temperature increase, the dew point temperature will increase.

  • B

    Dew point temperature is not affected by the air temperature.

  • C

    For unsaturated air, a decrease in temperature causes condensation which will decrease the dew point.

  • D

    The dew point temperature varies inversely with changes in the air temperature.

Warmer air can hold more water vapour than cold air, It can be imagined that a warm parcel of air is a bigger bucket than a cold parcel of air.

The dew point is the temperature the air needs to be cooled to (at constant pressure) in order to achieve saturation (= a relative humidity (RH) of 100%). In simple words, it is the temperature at which the air can no longer "hold" all of the water vapour which is mixed with it (the bucket has shrunk) - and some of the water vapour must condense into liquid water. The dew point is always lower than (or equal to) the air temperature.

Increasing or decreasing the temperature of an unsaturated parcel of air has no effect on its dew point. Once the air is saturated, a decrease in temperature causes condensation which will decrease the dew point.

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