q The air’s content of moisture can be measured by the pressure exerted by the water vapor in the air.
qThe total pressure
inside an air parcel is equal to the
sum of pressures of the individual gases.
qIn the left figure, the
total pressure of the air parcel is
equal to sum of vapor pressure plus the
pressures exerted by Nitrogen and Oxygen.
qHigh vapor pressure
indicates large numbers of water vapor
molecules.
qUnit of vapor pressure
is usually in mb.