The Complex World of Humidity and Temperature

During sunlight hours (minimal cloud) the water vapour in the air will absorb long wave IR (Green House Effect) from the sun and from the ground.
This will be radiated back in all directions.
The solar radiation will therefore be modified such that the wavelengths absorbed by the water vapour will be reduced depending on the effectiveness of the green house effect.
 However the same wavelengths radiated upwards will be more effectively "reflected" back down.

At night the solar input stops and the only radiation hitting the earth is that from GHGs So more water vapour = better "reflector"

Is this visible in the data previously used below.
Firstly data is limited and to get sensible results each point needs significantly more than one result to be significant.

Night time readings cannot include cloud coverage as this is not measured when dark
The former plots used either average or min/max values. The min max tend to plot one off anomalies. In the plots below 1st and 3rd quartile results have been used to improve this.

First a whole year all possible times with up to 9% opaque cloud cover

http://www.nrel.gov/midc/srrl_bms/

not sure why humidity so high!

Now in sequence 2 months at a time a couple of hours and up to 9% opaque cloud cover

Now for some night responses 2 months at a time

Conclusion?

• Well minimum temperature shows a increase with increasing water vapour (positive slope) over coldest period but turns to negative slope during warmer months
• The max temp during the night shows little change with water vapour.