The diagram above represents western California’s Sierra Mountains. Air generally moves from west (windward side) to east (leeward side). Assume that a parcel of air is forced to rise up and over the 4000-meter-high mountain (as shown). The DAR is 10°C/1000 m and the MAR is 6°C/1000 m. Assume that condensation begins at 100% relative humidity and that no evaporation takes place as the parcel descends.
The initial temperature of the parcel at sea level is 25°C, and the lifting condensation level (LCL) of the parcel is 2000 meters.
What is the dew point temperature? ______°C
At the dew point temperature how much water vapor can the air hold? That is, what is the maximum specific humidity? ____ grams
At 25°C how much water vapor can the air hold? That is, what is the maximum specific humidity? ____ grams
At 0m the air initially begins with 5.4 grams of water vapor.
What is the initial relative humidity at 0m?
At 4000m the air now only has 2 grams of water vapor and it has lost 3.4 grams of vapor, because the water turned into clouds.
At 0m on the leeward side the air still has 2 grams of water vapor.
How much water vapor can it now hold at 0m on the leeward side? _____ grams
What is the relative humidity at 0m on the leeward side? _______ %
Explain why the parcel is now warmer than it was at sea level on the windward side (what is the source of the heat energy).
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