insolation

noun

1. (uncountable, usually)The incident radiant energy emitted by the sun which reaches a unit area over a period of time, typically measured over a horizontal area at the Earth's surface or at the top of Earth's atmosphere.

   “The difference in insolation between north-facing and south-facing slopes can affect microclimates as much as hundreds of miles of north-south distance on level ground.”

2. (uncountable, usually)The rate of delivery of such radiation.
3. (uncountable, usually)The act or process of exposing to the rays of the sun, such as for the purpose of medical treatment, drying or maturing, as fruits, drugs, etc., or of rendering acid, as vinegar.
4. (dated, uncountable, usually)sunstroke.