Why do the operating wind turbines warm nighttime temperature?
This warming effect is most likely caused by the turbulence in turbine wakes acting like fans to pull down warmer near surface air from higher altitudes at night. Typically nighttime has a stable atmosphere with a warm layer overlying a cool layer. Enhanced vertical mixing mixes warm air down and cold air up, leading to a warming near the surface at night. Daytime often has an unstable atmosphere with cool air lying over warmer air. Turbulent wakes mix cool air down and warm air up, producing a cooling near the surface during the day. However, daytime mixing is already very large due to solar heating. Hence, the turbine-enhanced turbulent mixing may play a smaller role during the daytime.