Latitudinal effects
Intensity of insolation is not the same at all latitudes because earth is roughly spherical
Compare what happens to insolation passing through a screen, held perpendicular to radiation path, with an area = 1 m2
- Where Earth’s surface is perpendicular to radiation (near equator), insolation illuminates an area = 1 m2
- Where Earth’s surface is inclined ~45° to radiation (at 45° latitude), insolation illuminates an area = 1 m2 x (1/sin45°) = ~ 1.4 m2
- Where Earth’s surface is inclined ~30° to radiation (at 60° latitude), insolation illuminates an area = 1 m2 x (1/sin30°) = ~ 2 m2
Moving from the equator to the poles, insolation per unit area decreases uniformly