atmospheric moisture + thermodynamics: geog 2130

Latent heat

Heat energy of a phase change

Latent heat energy must be ADDED (ABSORBED) for phase changes from solid to liquid to gas

and RELEASED for phase changes from gas to liquid to solid

Deposition

Change from water vapor to directly solid (energy released)

Sublimation

Change from solid directly to water vapor (energy absorbed)

Specific heat

The heat capacity of a substance

Water has a ___ specific heat that land

Higher

(Meaning water warms more slowly and requires more energy to warm than land does)

Humidity is

The amount of water vapor in the air

Absolute humidity

Mass of water vapor in a given volume of air; Pv = mass / volume

(the density of water vapor)

Specific humidity is the

Ratio of the mass of water vapor in the air to the total mass of the air; q = mass H2O/mass of air

Mixing ratio is the

Ratio of the mass of water vapor in the air to the mass of the remaining dry air; w = mass H2O/ mass of dry air

Vapor pressure

partial pressure of water vapor in the atmosphere

Dalton’s law of partial pressure

P parcel = P N2 + P O2 + P H2O

Saturation vapor pressure

maximum vapor pressure that can be achieved at a given temperature and air pressure

Saturation:

Equilibrium condition where evaporation and condensation are in balance

Saturation Vapor Pressure:

pressure exerted by the water molecules when the air is saturated

When more H2O molecules are evaporating than are condensing, vapor pressure ___

Increases

When the same amount of H2O molecules are evaporating and condensing:

Vapor pressure and saturation vapor pressure are equal

Relative Humidity (RH)

RH = (actual/capacity) x 100

Capacity= air parcel volume

Actual= how much air parcel is water vapor

Higher temperature can hold __ water vapor

More

So greater maximum water vapor is possible