Key for Homework 4

 

  1. Determine the noon sun angle at the Tropic of Capricorn (23.5°S) on June 21.

    Noon sun angle = 90 - (distance between your latitude and the solar declination).

    Solar declination on June 21 is 23.5°N.

    Noon sun angle = 90 - ( 47° ) = 43°

     

  2. Is the sun ever directly overhead in Omaha (40°N)? Why or why not?

    No. The solar declination is never as far north as 40°N. The farthest north it ever reaches is 23.5°N.

     

  3. Answer "Review Question 1" on page 125 in your textbook.

    Since relative humidity is vapor pressure divided by saturation vapor pressure, two ways to increase the relative humidity to 100% would be to increase the vapor pressure (i.e., add water vapor by evaporation) or to decrease the saturation vapor pressure (i.e., lower the temperature).

     

  4. Answer "Review Question 5" on page 125 in your textbook.

    On the muggy night, the dewpoint was very high. When this air touched the cold floor of the arena, it cooled (by conduction) to the dewpoint temperature. Further cooling resulted in condensation of water onto the arena floor.

     

  5. What is the vapor pressure of an air parcel when the relative humidity is 50% and the saturation vapor pressure is 20mb?

    10 mb

     

  6. Why is it necessary for a cloud droplet to GROW?

    Cloud droplets are too small to fall to the earth's surface as precipitation. They would fall too slowly and evaporate too easily.

     

  7. Drizzle drops are very small. Does drizzle fall out of HIGH clouds or LOW clouds? Why?

    Drizzle falls out of LOW clouds. They obviously cannot be falling very far, because they would evaporate.

     

  8. Fill in the blanks in this paragraph: "The Bergeron process works because the saturation vapor pressure over ice crystals is slightly _______________ (higher or lower?) than the saturation vapor pressure over supercooled water droplets. Consequently, in a cloud, often the relative humidity is slightly __________________ (greater or less?) than 100% around ice crystals and slightly __________________ (greater or less?) than 100% around supercooled water droplets. Therefore the _________________ (ice crystals or water droplets?) grow and the ______________________ (ice crystals or water droplets?) evaporate. The cloud changes in such a way that now there are __________________ (many or few?) ___________________ (small or large?) ice crystals and ________________ (many or few?) ___________________ (small or large?) supercooled water droplets. Changing the sizes of the droplets and ice crystals in this way makes ___________________ (condensation or coalescence?) a much faster process."

    "The Bergeron process works because the saturation vapor pressure over ice crystals is slightly __LOWER_____________ (higher or lower?) than the saturation vapor pressure over supercooled water droplets. Consequently, in a cloud, often the relative humidity is slightly __GREATER________________ (greater or less?) than 100% around ice crystals and slightly ___LESS_______________ (greater or less?) than 100% around supercooled water droplets. Therefore the ___ICE CRYSTALS______________ (ice crystals or water droplets?) grow and the __WATER DROPLETS____________________ (ice crystals or water droplets?) evaporate. The cloud changes in such a way that now there are _____FEW_____________ (many or few?) __LARGE_________________ (small or large?) ice crystals and __MANY______________ (many or few?) __SMALL_________________ (small or large?) supercooled water droplets. Changing the sizes of the droplets and ice crystals in this way makes ___COALESCENCE________________ (condensation or coalescence?) a much faster process."

     

  9. Answer "Review Question 8" on page 125 in your textbook.

    "Cirro" clouds are high. "Nimbus" clouds have precipitation. No precipitation could ever fall from a "high" cloud without evaporating.