3·The table below gives the maximum amount of water vapor that could be present

Question

3·The table below gives the maximum amount of water vapor that could be present in the air at varibus air temperatures. Use the table to answer the following questions. Air Temperature C Air Temperature Saturation Vapor Pressure (millibars) 3.7 4.6 20 25 7 10 16 24 29 32 10.2 45 50 60 12.3 85 41.0 48.1 a. The air temperature and the dewpoint temperature of the air are 75°F. Using the table above, the pressure associated with the actual amount of water vapor in the air _(mb) and the pressure when the air is filled to eapacity with water vapor (mb), respectively. What is the relative humidity of the air? is 1s b. The air temperature is 24°C and the dew point temperature is 60°F. What is the relative humidity of the air? Show the solution. c. If the pressure of the moisture content of the air is 6.9 mb and the air temperature is 10°C, in what temperature should the air must be cooled in order to saturate the air? d. At 10°C a particular air parcel is saturated with water vapor. If the temperature of this air parcel increases to 24°C, while keeping the water vapor constant, one may conclude that the dewpoint temperature is about e. If the moisture content of the air is 17.7 mb and the air temperature is 29°C, what amount should the moisture content be increased in order to saturate the air?

Explanation / Answer

a.if the water vapor pressure in the air is 10.2 millibars (mb), dew will form when the ground reaches 45 degrees Fahrenheit (F). The relative humidity for air containing 10.2 mb of water vapor is simply 100% times 10.2 mb divided by the saturation vapor pressure at the actual temperature. For example, at 75 F the saturation vapor pressure is 29.6 mb, so the relative humidity would be

RH = 100% X (10.21 / 29.6) = 34%

b. Given the following data,

1. air temperature in degree celsius = 240C

2. dew point temperature in degree celsius = 150C

3. The following set of formulas assumes a standard atmospheric pressure. These formulas will calculate saturation vapor pressure(Es) and actual vapor pressure(E) in millibars.

(i) Es=6.11*10.0**(7.5*Tc/(237.7+Tc))

(ii) E=6.11*10.0**(7.5*Tdc/(237.7+Tdc))

Applying the formula (i),

Es= (6.11*10)*(7.5*24/(237.7+24)) = 42 mb

Applying the formula (ii),

E = (6.11*10)*(7.5*15/(237.7+15)) = 27.2 mb

Once you have the saturation vapor pressure and the actual vapor pressure, relative humidity can be computed by dividing the actual vapor pressure by the saturation vapor pressure and then multiplying by 100 to convert the quantity to a percent.

(4) Relative Humidity(RH) in percent =(E/Es)*100

                                                      RH% = (27.2/42.0)*100 = 65%

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