The seasonal changes in the diurnal cycle are very much as expected, with a tiny diurnal cycle in December giving way to a substantial daily oscillation by February. According to the hourly means, the coldest hour of the day in December is 7 am AKST, which is well before the sun rises; but there is less than 0.5 °F difference from midnight to 11 am.
We could also look at the frequency with which each hour of the day records the lowest or highest temperature, and examine some histograms based on those results, but I'll leave that for another time.
As we're on the topic of short-term temperature fluctuations, it's worth noting that these have been very large in Fairbanks lately. The plot below shows the 2m temperature trace from UAF's North Campus, near Smith Lake, over the past 4 days (with a period of missing data in the middle). The 2m temperature rose from -39.4 °F on Sunday to +47.2 °F yesterday, a rise of 86.6 °F in three days. Looking at the official Fairbanks history since 1930, only two occasions saw a larger 3-day temperature rise, and both of those were in January.
At Fairbanks airport, the recent 3-day rise was 84 °F (-37 to
The diurnal temperature range has also been very large in recent days: 46 °F yesterday, which is equivalent to the largest that is typically observed in any given year. March is by far the most common month for observing the year's largest diurnal temperature variation in Fairbanks.
Thank you Richard for the analysis. Yes it's cold just before dawn and often some surface movement of cold air happens around that time.
ReplyDeleteHere's a new offering of daily forecast conditions for Fairbanks from the NWS. Shows a similar trend as above:
http://forecast.weather.gov/MapClick.php?lat=64.4822&lon=-147.9059&unit=0&lg=english&FcstType=graphical
Gary
Why is the spring in Fairbanks so much warmer than other locations in interior Alaska? Places like Tok and Galena are located at lower latitudes but they don't warm up as fast.
ReplyDeleteThanks for the question. I'll post something about this soon. I've been snowed under with other projects and a bout of the 'flu recently.
DeleteAmong several factors Fairbanks is subject to warmth due to:
ReplyDeleteLots of dark roads and buildings absorbing solar heat in a sheltered spot. Spring Sun warms them up. Plus there's heat from power plants, furnaces and vehicles.
It's location north of the Alaska Range puts it in the path of occasional warm southerly air flow caused by winds forced over mountains. The air from the south is dried than later heated by compression during descent. The heated north to south flow flushes out the cold and warms us up...like forecast for today and tomorrow 3/26-27/2015 with temps in the 40's and 50's.
It's lower in elevation than Tok by about 1200'. The higher you go normally the colder it gets.
Galena has no heated mountain down flow to cause warmth, has fewer local sources of heat, and is closer to the coast which typically tends to be cooler than Interior Alaska.
Gary
HI Gary,
DeleteThanks for the detailed explanation about the southerly air flow. I learned so much from this blog by reading your comments!
I'm just an observer of nature and not a trained weather forecaster. In general many towns to the north, south, east, and west of Fairbanks can be cooler at certain times of the year. It's called 'Fair-banks' for several reasons.
DeleteI didn't mention above the effect that warm air above us has on the temperature at the surface. Weather analysts send up a balloon with temperature and other sensors and look for changes as the balloon ascends. Based on the results they forecast how warm it might get through the day at the surface...generally the warmer above the warmer below.
Some's magic and some's science, and it's all fun to watch it happen.
Gary