A) What is the saturated vapour pressure of an air parcel at a temperature of 15

Question

A) What is the saturated vapour pressure of an air parcel at a temperature of 15oC?

B )An air parcel at 15oC has an absolute humidity or actual vapour pressure of 4 g/m3. What is the relative humidity of the parcel of air?

C) What is the approximate dew point temperature of the parcel of air?

D) Using the same parcel of air, assume that it cools to 5oC on a cool autumn afternoon in Winnipeg and maintains the same actual vapour pressure of 4 g/m3. What is the relative humidity at this time?

Thank you!

Explanation / Answer

A. Saturate vapour pressure of air parcel at temperature-15oC = 10mb

B. Relative Humidity= (Actual vapour pressure/Saturation vapour pressure)*100%

Saturation vapour pressure,ew = 17mb=1700Pa

Temperatute, T=15oC = 288K

Absolute humidity,AH = actual vapour pressure(e)/(Specific gas constant(Rv)*T)

0.004kg/m3 = actual vapour pressure(e)/461.5*288

Actual Vapour pressure = 531.648Pa

Relative Humidity, RH = (531.648Pa/1700Pa)*100% = 31.273

C) Dew point temperature, Td = T - ((100 - RH)/5)

Td = 288-((100-31.273)/5) =274.25K

D) Actual vapour pressure, e = 531.648Pa

Temperature=5oC=278K

Saturation vapour pressure, ew = 870Pa

Relative humidity, RH = (Actual vapour pressure/Saturation vapour pressure)*100%

= (531.648/870)*100%

= 61.10

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