It is well known that the intensity of solar radiation at the ground surface varies with the geographic location, the time of day and the season of the year.
Figure 2 shows daily variation characteristics of the solar radiation intensity in RCEES in different seasons.
The results indicated that the solar radiation intensity had a peak value at noon, and was 0 during the period from sunset to sunrise the next morning.
Naturally, the times of sunrise and sunset and the maximum value of the solar radiation intensity are different in each season.
The longest solar radiation time and maximum intensity appeared in summer.
In addition the solar radiation intensity is very low on a cloudy day compared with on a sunny day.