Do you realize that our body is subjected to a lot of air pressure. As one moves up the air gets verified and one feels breathless.
The weight of a column of air contained in a unit area from the mean sea level to the top of the atmosphere is called the atmospheric pressure. The atmospheric pressure is expressed in units of mb and Pascals. The widely used unit is kilo Pascal written as hPa. At sea level the average atmospheric pressure is 1,013.2 mb or 1,013.2 hPa. Due to gravity the air at the surface is denser and hence has higher pressure. Air pressure is measured with the help of a mercury barometer or the aneroid barometer. The pressure decrease with height. At any elevation it varies from place to place and its variation is the primary cause of air motion, i.e. wind which moves from high pressure areas to low pressure areas.