4. Recall that relative humidity is a function of the actual vapour pressure and the saturation vapour pressure (text, p. 91):
where VP = vapour pressure, and W = mixing ratio. The subscript s refers to the saturation vapour pressure or mixing ratio. Compare the actual water content of the air over the sunny Sahara with that of a blizzard in Baffin Bay. In the Sahara, use a temperature of 40°C and a RH of 10%. Use mixing ratios (W/Ws) for your calculations, so that you will end up with water content in g/kg, which is more meaningful than mb here. Calculate the mixing ratio by reversing the above equation and solving for W. Determine the saturation mixing ratio by referring to Table 4-1 in the text. Then do the same for the Baffin Bay blizzard, where the air temperature is -10°C and the RH = 100%.
[2 marks]
5. In the tropical rain forest latitudes, intense solar heating causes air to rise along a zone sometimes referred to as the “thermal equator” or the “inter-tropical convergence zone”. You know that the active tropospheric part of the atmosphere is a maximum of 18 km at the equator. Suppose the air at sea level has a temperature of 30°C. What would be its temperature at 18 km assuming it rises by the dry adiabatic lapse rate?
[2 marks]
Obviously (I hope) the air never gets that cold! Why not?
