I think he is unaware that water vapor is the only one of the so called greenhouse gasses that can absorb, and actually retain energy....
That's not true. All gasses, greenhouse or not, hold thermal energy. With water you are referring only to it's extra ability to change phases.
..it has to do with water being the only substance that we know of that can change phases in the open atmosphere....it is warmer in humid areas than it is in the desert due to the fact that humidity (water vapor} has actually stored energy and since there is little humidity in the desert, it gets cold very quickly at night...there being nothing to absorb and hold the energy still radiating from the earth.
You have a contradiction here. You are referring to water as having latent energy which is only manifested during a phase change. (Vapor changing to snow or hail, water evaporating, snow melting, etc.) In a desert, water is not undergoing any phase change, so you can't use "phase change" in any statement about what's happening in a desert unless it rains. You will have to come up with a different reason for the climate in a desert.
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