Atmospheric Pressure And Winds Flashcards
What is atmospheric pressure
The pressure exerted by the weight of air in the atmosphere at the surface of the earth
What is the unit of atmospheric pressure
The millibar (mb) and it is measured using a barometer
What is the average atmospheric pressure at sea level
1,013 mb
What are isobars
Join points of equal atmospheric pressure on a weather map by lines
Where is the pressure greatest
The layers of the atmosphere closest to the ground surface have the greatest weight acting upon them, so pressure is greatest here
Air pressure and altitude
Air pressure decreases with altitude
Why does atmospheric pressure vary horizontally
Because it is a direct function of temperature
Temperature rises
Air expands and rises by convection, and pressure decreases
Temperature falls
Air contracts and becomes denser, causing an increase in pressure
Where does high pressure occur
Where air is descending and is associated with dry weather.
Air warms as if descends, leading to the evaporation of most water vapour
Where do low pressures occur
Where air is rising
Generally linked to precipitation and windy conditions
Air cools as it ascends and cannot hold as much water vapour
= rain drops = clouds at condensation level
