Ch. 15,  p. 437, #2-6, 8-9

2.  After studying Table 15.1, write a generalization relating temperature and the capacity of air to hold water vapor.

A. As temperature increases, the capacity of air to hold water vapor increases (at an increasing rate).

3.  How do relative and specific humidity differ?

A.  Specific humidity incicates the amount of water vapor in the air and is expressed as the weight of water vapor per weight of air.

4.  Referring to Figure 15.6, answer the following questions and then write a generalization relating changes in air temperature to changes in relative humidity.
a)  During a typical day, when is the relative humidity highest?  Lowest?

A.  It is highest near sunrise and lowest during mid-afternoon.

b)  At what time of day would dew most likely form?

A.  When the temperature was lowest and the relative humidity highest, that is, near sunrise.

5.  If the temperature remains unchanged and the specific humidity decreases, how will relative humidity change?

A.  With a constant specific humidity, an increase in temperature causes a decline in relative humidity, and a drop in temperature causes a rise in relative humidity.

6.  On a cold winter day when the temperature is -10o C and the relative humidity is 50 percent, what is the specific humidity (refer to Table 15.1)?  What is the specific humidity for a day when the temperature is 20oC and the relative humidity is 50 percent?

A.  1 gram per kilogram of air; 7 grams per kilogram of air
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8.  Using the standard tables (Tables 15.2 and 15.3), determine the relative humidity and dew-point temperature if the dry-bulb thermometer reads 16oC and the wet-bulb thermometer reads 12o C.  How would the relative humidity and dew point change if the wet-bulb thermometer read 8oC?

A.  62% relative humidity; dew point 9o C; 29% relative humidity; dew point -1oC

9.  On a warm summer day when the relative humidity is high, it may seem even warmer than the thermometer indicates.  Why do we feel so uncomfortable on a "muggy" day?

A.  Since the relative humidity is high, there would be a minimum of evaporation of perspiration, the body'g natural cooling system.


Last update 3/15/2003

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