Saturday, January 5, 2019

Colder Statewide, Snowy December in Bettles

A deep winter chill has descended upon much of Alaska this weekend, with temperatures dropping well below zero in the usual cold spots.  So far Fairbanks airport has dropped to -34°F, which is colder than anything that occurred last winter.  Of course it is a rare winter in Fairbanks that doesn't drop to at least -35°F at some point.

A few other cold spots today are:

Chicken  -49°F
Fortymile River HADS   -43°F 
North Pole  -39°F
Salcha RAWS  -38°F

The Fortymile River HADS site (on the Taylor Highway) did not rise above -40°F today, and with the cold expected to deepen somewhat in the next few days, I'd be very surprised if Chicken doesn't crack -50°F.  Only two winters in Chicken's climate record (1996-present) have failed to reached -50°F, and -60°F or colder occurs in about half of all winters.

Alaska's snow pack is below normal in many places, but one area with plenty of snow is the upper Koyukuk region; observers from Bettles up to Wiseman are reporting 30" or more of snow on the ground (click to enlarge maps below).

Remarkably, Bettles had its snowiest calendar month on record in December, with 62" of snow.  The typical annual snowfall in Bettles is close to 90" - fairly high for an interior valley location - but nevertheless 60" in a month is a lot.

A scatter plot of December snowfall and average temperature in Bettles shows a slight positive correlation, as the coldest months tend to be drier than normal; this is partly because the coldest Arctic air masses hold little moisture in winter, and partly because clear skies (associated with high pressure and dry weather) produce sustained temperature inversion and cold conditions at this time of year.

As we've noted before, the situation is quite different in Fairbanks owing to the effect of dry chinook winds from the south.  The proximity of the Alaska Range means that the warmest months, which are dominated by southerly flow, also tend to be dry, and so the snow-temperature plot shows a peak in snowfall at near-normal temperatures.


  1. --This comment is intended for article about CERES radiation data. Does not seem to be posting to right place.--
    I would have thought that ceres (satellite) data of radiated longwave to space would indicate only temperature at the top of the atmosphere, only indirectly reflecting temperatures at the earth's surface. After all, the sun's core has a temperature of millions of degrees, but its radiation to space is the blackbody spectrum of the 5700 degrees at the top of the solar atmosphere.
    Most of the infrared from earths surface is reabsorbed by water vapor and CO2 before it can be radiated to space; as GHG concentrations increase the altitude by which most of this radiation is absorbed will lower, heating the near-surface without heating the top of the atmosphere; basically shifting heat distribution downwards, even if average temp of air column remains same.

    1. Thanks for the comment. Yes, the satellites observe longwave emitted at various heights, depending on wavelength and the distribution of radiatively active components like clouds and water vapor. The CERES surface longwave data that I discussed are obtained from a radiative transfer model/calculation, so it's an estimate rather than a direct measurement.