Some problems about geography

1 high latitude, relatively far from the sun; In addition, the height angle of the sun is small, and the sunlight is oblique, so the route through the atmosphere will be longer, and the natural weakening effect will be greater; Also, the height angle of the sun is small, and less sunlight is obtained per unit area (imagine the situation of flashlight scattering).

Here I only describe the situation in the northern hemisphere (the southern hemisphere is just the opposite). At the beginning of the vernal equinox, extreme days began to appear in the Arctic Circle, and then the range of extreme days became larger and larger. On the summer solstice, all the Arctic circles are extreme days, and then the range of extreme days becomes smaller and smaller. Until the autumnal equinox, there was no extreme day in the Arctic Circle, and the scope of extreme night began to appear, and it was getting bigger and bigger. On the solstice of winter, all the Arctic circles are at midnight, and then they become smaller and smaller until the vernal equinox. (Because of the yellow-red intersection)

The vernal equinox doesn't necessarily start in spring, and it hardly does. The vernal equinox refers to March 2 1 day, when the sun shines directly at the equator. In China, spring begins at the beginning of spring, and beginning of spring is a solar term, usually not March 2 1.