1. Express numerical answers to 1 decimal place, unless otherwise indicated. Spe
ID: 113940 • Letter: 1
Question
1. Express numerical answers to 1 decimal place, unless otherwise indicated.
Specific Humidity measures the vapour content of air by the mass of water vapour (grams) in a kilogram of air. Figure 1 below represents the maximum specific humidity of air at different temperatures. It shows that a kg of air can hold a maximum specific humidity of 26.5 g at 30 °C, 15 g at 20 °C, 7.5 at 10 °C and 4 g at 0 °C. If a kg of air at 30 °C has a specific humidity of 12 g, its relative humidity can be calculated as follows:
12g / 26.5g = 0.453 x 100 = 45.3 %
a) What is the relative humidity of an air parcel that is 20 °C and has a specific humidity of 4 g of water per kilogram air?
b) What is the relative humidity of the same air parcel if it is cooled to 0 °C?
c) What is another term that weather people would use to describe the air parcel in b, given its relative humidity?
Explanation / Answer
1 a) What is the relative humidity of an air parcel that is 20 °C and has a specific humidity of 4 g of water per kilogram air?
Given maximum specific humidity at 20 °C = 15 g
Relative humidity = (Specific humidity at 20 °C / Maximum specific humidity at 20 °C )*100
= (4/ 15) *100 = 26.7 %
b) What is the relative humidity of the same air parcel if it is cooled to 0 °C?
Given maximum specific humidity at 0 °C =4 g
Relative humidity = (Specific humidity at 0 °C / Maximum specific humidity at 0 °C )*100
=(4/4) * 100 =100 %
c) What is another term that weather people would use to describe the air parcel in b, given its relative humidity?
When air has 100 % Relative humidity ,weather people use the term totally saturated with water vapor .
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