Define air pressure. What influences air pressure in the open atmosphere?

Define air pressure. What influences air pressure in the open atmosphere?

Answer:

-Air Pressure - Average force exerted on a unit area by molecular collisions
-Factors Influencing Air Pressure: (If all else is equal, in the open atmosphere). :

->As altitude increases, pressure decreases 

->As amount of water vapor increases, pressure decreases 

->As temperature increases, pressure decreases 

->Pressure 

->Decreases at the surface where air is rising 

->Increases at the surface where air is subsiding