what about the simple answer
you have already posted correlation that it is warmer when there is no cloud cover.
maybe there is no cloud cover because its warmer.
Cloud formation is dependant on the temperature of the air they form in. It requires cool air to cause condensation.
Certainly the ocean temp adds to the moisture content of the air, but it doesn't matter how much moisture inflow there is, if the temperature is to high for cloud formation.
