why is the difference in solar receipt between 60N and 30N greater in the winter than in the summer?

Answer 1

At noon on the summer solstice, the sun's zenith angle is 37 deg at 60 latitude and 7 deg at 30 latitude. The noon solar irradiance has a ratio
cos 7/cos37 = 1.24, and the sun is up much longer at the more northern latitude. The net result is very little dfference in total sunshine (assuming no clouds).

At noon on the winter solstice, the sun has zenith angle at 83 degrees at 60 N and 53 degrees at 30 latitude. The noon solar irradiance ratio is cos 53/cos83 = 4.93, AND the sun is up longer at the lower latitude.

The net result is a much larger solar 'receipt' difference (also called "insolation" difference) in the winter.

Answer 2

What latitude experiences the smallest variation in insolation during the year? What explains this pattern?