Thursday, February 17, 2011

Diurnal Temperatures and the Sun

It is nearly eight weeks past winter solstice now, and sure is enjoyable to have more than twice the daylight of late December. However, the sun is still at quite a low angle: only about 13 degrees above the horizon at solar noon today. The result is that direct heating from the sun is still not the primary factor in temperature changes in Interior Alaska. The plot at the right shows the hourly temperatures for the past several days from here on Keystone Ridge, with the vertical lines marking midnight. On most days, the high or low temperatures have occurred close to midnight. There is of course nothing special about midnight. Whatever time you pick for the break in the climatological day will tend to have the extremes when solar heating is not an important driver of temperature changes.

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