Daily Temperature Variations

A characteristic of life in the north is the small daily range in air temperature, at least compared to regions to the south.

The main reason for the relative constancy of air temperature is the comparatively small change in solar elevation each day at high latitude. In the extreme, above the Arctic Circle, the sun does not come up at all in midwinter and so provides no warming heat. In midsummer, the sun scoots around the sky without changing its elevation angle by more than a few tens of degrees.

When the sun is low in the sky a large fraction of the energy in sunlight is absorbed by the atmosphere. Also, the sunlight that does get through strikes a larger area of the ground. Consequently a unit area of ground surface receives far less solar energy when the sun is near the horizon than when the sun is high overhead.

Even when the sun is directly overhead (elevation angle 90°), only about 60% of the sun's energy impinging upon the earth's atmosphere reaches the ground. That percentage is nearly halved by the time the sun drops to 45° above the horizon.

When the sun is within 10 degrees of the horizon, there is such minor heating at the base of the atmosphere that on northern midwinter days we see little noontime warming.