V. Moisture

A. Hydrologic cycle (Fig. 4-1)

evaporation and condensation have the greatest impact on weather

B. 3 states of water

warming processes (release energy to surroundings)

<<<<<<<<<<<< deposition <<<<<<<<<<<<

<<< freezing <<<<< <<<<<condensation<<<

ice

water

vapor

(low energy)

 

(high energy)

>>>>>>>melting>>>>>>>>evaporation>>>>>>

>>>>>>>>>>>>>> sublimation >>>>>>>>>>>>>>

cooling processes (absorb energy from surroundings)

 C. Humidity
  1. basics (Fig. 4-6)
    1. vapor pressure
    2. saturation
  2. absolute humidity (mass of water in a given volume of air (gm/m3)
  3. relative humidity - (percent) Temperature dependent (Fig. 4-7

    4. amt. water vapor in air x 100
    max. capacity
    1. max. capacity of air to "hold" water depends on Temp
    2. warm air "holds" more water than cold air
    3. as T increases, relative humidity decreases (FIG. 4-8)
    4. as T decreases, relative humidity increases
    5. daily variations as temp. changes (Fig.4-9)
    6. effect of ocean temperature on vapor content of air
    7. when RH = 100% reach saturation and condensation overwhelms evaporation and creates fog, frost, dew, clouds

  4. measurement of RH and dew point with a sling psychrometer (Appendix C)
D. Dew point (temperature)
  1. related to absolute amount of moisture in the air
  2. temperature at which RH=100%
  3. occurs when amt. water vapor in the air = max capacity
  4. indicates the amount of moisture in the air (i.e. cold air with high RH and low dew point contains less water vapor than hot air with low RH and high dew point)
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