Variation in Solar Intensity With Latitude

Variation in intensity of solar radiation with latitude. For simplicity, we  depict two equal parcels of incoming radiation on an  equinox, a day when incoming rays are perpendicular to Earth’s axis. Rays that fall on high latitudes (a) pass through more atmosphere (blue) than those that fall near the equator (b). Compare the length of the green lines. Atmosphere is not to scale. Also, energy in the rays that fall at the high latitude is dispersed over a greater area than energy that falls on the equator. Compare the length of the red lines.