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Labs 5 &amp; 6

# Labs 5 &amp; 6 - Lab 5 Atmospheric Moisture Part 1...

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Lab 5: Atmospheric Moisture Part 1: Thermodynamic Principles (1)Air cools as it rises. Assume that an unsaturated air parcel cools at the rate of 10 degrees Celsius for every kilometer it rises in the atmosphere. If an air parcel’s temperature initially is 15 degrees Celsius and it is forced upward 1 km before it stops rising, what is its final temperature? 5 degrees Celsius (2) If a parcel were to rise above the level where its relative humidity (RH) is 100%, what happens to the water in the air parcel? What happens to the parcel’s relative humidity as it continues to rise above that level? When the parcel reaches 100% RH, it will condense some moisture to form liquid droplets. At this point, the RH is still 100% and it remains at 100% until the parcel descends or is somehow mixed with drier air. (4) Table 1 contains temperature observations from Phoenix, AZ and Miami, FL. Explain why a large difference exists between the two sets of observations. Note the differences in the daily range in temperature (i.e., range = maximum –minimum) Phoenix, AZ R= T max – T min (range) 30 = 113 -83 Miami, FL R= T max - T min (range) 14 = 95 – 81 In Phoenix, the air is very dry as indicated by the low dew point temperature and consequently the low relative humidity in comparison with the dew point and consequently the relative humidity in Miami. Therefore, much of the heat gained during the day in Phoenix is lost at night since there is a smaller amount of moisture in the air to absorb the long wave radiation. The higher moisture content in Miami will absorb more of the long wave radiation and re-emit it toward the earth thereby causing less of a temperature difference between the high and low temperature. (6) Assume that the skies were clear at both Phoenix and Miami for the observations in Table 1. Also, assume that both cities received the same amount of incoming solar radiation at the earth’s surface. If the ground in Miami was moist and the ground in Phoenix was dry, how can the moisture of the ground help explain the observed temperatures? (Hint: Think about how the incoming solar energy would be partitioned between latent heat and sensible heat.) (7) If virga were seen below a cumulonimbus cloud, would the air just below cloud base (i.e. within the virga) be cool or warm? If the virga, an evaporating streak of precipitation, were seen below the cumulonimbus cloud, the air just below the cloud would be cool. Even though the lower part of the cumulonimbus cloud is the warmer part of the cloud, as the rain from the virga is changed from a liquid to a vapor form, it removes heat from the air.

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