F.4 Geo:Duration of sunshine
When the overhead sun is in 23.5N(Northern Hemisphere), why the duration of sunshine is longest at 90N?
- 1 decade agoFavorite Answer
When the overhead sun's on the 23.5 degrees north(on the summer solstice, 21/3), it just implies that the angle of sun on the Tropic of Cancer is the largest (90 degrees) of anywhere else on the Earth. Therefore, the insolation there is also the MOST CONCENTRATED at noon, regardless of other factors, say toporgraphy, cloud cover. It deals nothing with the duration of sunshine.
The determining factor of the duration of sunshine lies on Earth's axial tilt or obliquity which is 23.5 degrees or more specifically 23.44 degrees. Owing to its obliquity, chances are that there are 24-hour insolation received on the North Pole (the summer solstice) and the South Pole (the winter solstice), when the respective hemisphere tilts towards the sun to its maximum extent.
However, on the Tropic of Cancer or the Tropic of Capricorn, there is 12-hour daytime.