Homework for Chapter 5 - Atmospheric Moisture

Questions 1 and 2 will be turned in for a grade. Questions 3-10 will be discussed by the discussion groups in class so please look them over before the discussion session.  

SHOW ALL WORK , CIRCLE THE CORRECT ANSWER, PLEASE BE NEAT AND STAPLE YOUR HOMEWORK!

ALSO, PLEASE USE A SPREADSHEET FOR ALL GRAPHS

Follow the Problem solving steps discussed in class

1. It can be shown that the saturation vapor pressure (e_s) depends only on temperature:

where e_o = 6.11 hPa and T_o = 273 K are constant parameters. R_v is the gas constant for water vapor and is equal to 461 JK^-1kg^-1. L is the latent heat of evaporation if water is present or the latent heat of deposition if ice is present. T is the temperature in Kelvin

a. For water, create a plot of e_s versus temperature for T=250 K to 273 K. Make sure e_s is on the y axis and temperature is on the x axis.  How does e_s depend on temperature?

b.  On the same graph, plot e_s versus temperature for ice.

c.  Is e_s  larger for ice or for water?

2.  Given a parcel of air having a temperature of 20 degrees C and relative humidity of 50% find:

a. saturation vapor pressure

b. vapor pressure 

c. heat index

d.  If the temperature of the air increased to 40 degrees C will the air feel more or less humid?  Explain.

3. Would you expect water in a glass to evaporate more quickly on a windy, warm, dry summer day or on a calm, cold, dry winter day? Explain.

4. How can frozen clothes "dry" outside in subfreezing weather? Explain.

5. Explain how and why each of the following will change as a parcel of air with an unchanging amount of water vapor rises, expands, and cools: (a) absolute humidity; (b) relative humidity; (c) actual vapor pressure; (d) saturation vapor pressure

6. Where in the U.S. would you go to experience the least variation in dew point from January to July?

7. Suppose the dew point of cold outside air is the same as the dew point of warm air indoors. If the door is opened, and cold air replaces some of the warm inside air, would the new relative humidity indoors be (a) lower than before, (b) higher than before, or (c) the same as before? Explain your answer with the aid of a diagram

8. On a warm, muggy day, the air is described as "close". What are several plausible explanations for this expression?

9. Outside, on a very warm day, you swing a sling psychrometer for about a minute and read a dry-bulb temperature of 38°C and a wet-bulb temperature of 24°C. After swinging the instrument again, the dry bulb is still 38°C, but the wet bulb is now 26°C. Explain how this could happen.

10. Why are evaporative coolers used in Arizona, Nevada, and California, but not in Florida, Georgia, or Indiana?

11. Devise a way of determining elevation above sea level if all you have is a thermometer and a pot of water.

EXTRA CREDIT: Given two parcels, one is dry containing 78% N2, 21% O2, and 1% AR while the other is moist, containing 78% N2, 21% O2, 0.5% AR, and 0.5% H2O. Show that the dry parcel has a larger density than the moist parcel.