1. Latitude. The more high latitudes, the shorter the altitude angle of the sun, and the shorter the sunshine time.

2. Seasonal changes. For the northern hemisphere, during the summer solstice, the sunshine duration is the longest in a year, and there are extreme days in the north of the Arctic Circle, but the opposite is true in the southern hemisphere.

3. altitude. At high altitude, the sunshine time will be longer, such as the Qinghai-Tibet Plateau in China.