Objective Comments and Analysis - All Science, No Politics
Contributions by Richard James and Rick Thoman
Saturday, October 29, 2011
Meteorological Winter Begins
The power of the waning sunshine was in evident Friday in Fairbanks-land. With no winds and no more than some cirrus, the morning inversion could not quite break, resulting in high temperatures Friday afternoon slightly lower than in the hills (high of 25F at Keystone Ridge, 22F at the Airport, 21F at Goldstream Creek). I hereby declare meteorological winter underway. This is quite important: I have to know what tags to include on these posts :)
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What is a Meteorological Winter?ReplyDelete
I was being a bit tongue-in-check, but in this situation, with fair skies and no significant wind on Friday, the fact that high temperatures were cooler in the valley than at elevation is a useful of the start of winter in Interior Alaska. It illustrates how little solar heating we're now receiving. For comparison, the overall average difference in July between Keystone Ridge (1600' MSL) and the airport (434' MSL) 4 degrees cooler on the ridge than valley, and that includes all days, not just sunny dry days.ReplyDelete
So, to more succinctly answer your question, here I defined meteorological winter in Interior Alaska to be the time of year when near full sunshine is not enough to break valley based inversions.ReplyDelete
Why is North pole always colder than Fairbanks? Thanks
Well, North Pole isn't always colder than Fairbanks, but it often is, especially for daily low temperatures.ReplyDelete
First, even more so than Fairbanks, North Pole is a flat land with lots of old sloughs and channels of the Chena and Tanana Rivers that provide good places for cold air to pool.
Second, there hardly any human development to the east and northeast of North Pole, while to the northeast of the Fairbanks Airport is, well, Fairbanks City. This is important in winter because the prevailing drainage flow of air is from higher to lower elevations, which in both cases is (north)east to (south)west.
Third, the North Pole is in "collection" area for cold air draining down the Chena River valley and far from any significant ridges. This helps keep wind speeds in North Pole very low in winter. The Fairbanks airport, in part influenced by nearby Chena Ridge, sometimes gets more wind in the winter than North Pole, which allows for more mixing of air, which keeps it from being quite as cold as North Pole.
Thanks for reading, hope this helps.