why does the atmospheric pressure usually decrease when the air becomes more humid??

Question

helpp plzzzz..

Answer 1

When air becomes more humid,it contains more water vapour.Water vapour is a gas which is lighter than air.So a mixture of water vapour and air(moist air) becomes lighter than dry air.As atmospheric pressure is the weight of the air column per unit area,the pressure decreases when humid air is there over a place.

Answer 2

Humidity requires heat (from the Sun) to vaporise the water. Warm, moist air rises because it's less dense than cold dry air. If air is rising in your vicinity then the overall pressure of the air near you must be decreasing. So low pressure areas are caused by rising warm (moist) air. High pressure areas, on the other hand, are caused by sinking cold (and dry) air.

That's why low pressure areas are usually associated with heavy cloud, rain and lots of wind (as more air is drawn into the rising air stream). High pressure areas are usually cloud-free, clear and with mild or even no wind.

Answer 3

Because humid air is less dense than dry air