While the North Pole and Eielson areas aren't always colder than Fairbanks, that is often then case in the winter (when there is not a Chinook) and for summertime low temperatures.
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.
Thank you for taking time to answers questions from your some of your most avid fans and readers. I thoroughly enjoy reading this blog, it's like my daily dose of something addictive.
Happy to helpReplyDelete
Thank you for the many intereseting posts about interior weather and climate. I have recently reviewed wind direction data collected at the North Pole Elementary School by FNSB, and was struck by the near complete absence of wind from the northern quadrant. I am wondering how to reconcile that observation with your observation about the prevailing drainage flow in Fairbanks and NP being from the NE to SW. Your comment is most welcome.
Thanks for your question. Was this from over this past winter?
My guess would be that with frequent strong inversions, while the cold air drainage is down valley, the speeds in North Pole are below the start-up threshold for the anemometer, so are reported as "calm". You can sometimes see the drainage down the Tanana from Fairbanks from the Parks Highway monument above Ester, with the ice fog flowing down valley, even though the surface wind speeds are "calm". Of course, once the sun starts to come back then local circulations develop, so that afternoon winds trend to be more southwesterly, flowing into the hills. Rick