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.