3. The winds are westerly off the Pacific Ocean and flowing into and up the Sier

Question

3. The winds are westerly off the Pacific Ocean and flowing into and up the Sierra Nevada Mountains. The air flowing off the ocean has a pressure of 1000 mb, a temperature of 25°C, and a dew point of 15°C. The top of the Sierra Nevada Mountains is approximately 2.2 km above sea level. a. Assuming adiabatic lift, what will be the temperature of the sea level air parcel after it rises to the top of the mountain? Explain how you arrived at your answer. b. Will the lifted air parcel be saturated by the time it reaches the top of the Sierra Nevada Mountains? Why?

Explanation / Answer

a.Since the air mass is rising to the top of Sierra Nevada mountain. The rising air mass will initially cool at the dry adiabatic lapse rate of 10 degree celsius/km. Since the initial temperature of the air mass is 25 degree celsius and the elevation of the mountain is 2.2 km above sea level. On reaching the 1km elevation above sea level the temperature of the air mass will be 15 degree celsius. The air has now become saturated since it reached the dew point temperature of 15 degree celsius. From this level the saturated air will rise at the moist adiabatic lapse rate of 6 degree celsius per km. On reaching 2.2 km which is the top of the mountain, the temperature of the air mass will be 15-7.2=.7.8 degree celsius.

b. The air mass rises initially with a rate of cooling of 10 degree celsius per 1000 m. Since the initial temperature of the air mass is 25 degree celsius so the air becomes saturated when it reached the 1000 m level. Now the air has reached its reached its dew point temperature of 15 degree celsius and continues to rise at the saturated adiabatic lapse rate of 6 degree celsius per km towards the top of mountain. So the lifted air parcel will be saturated when it reaches the top of Sierra Nevada mountain.

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