Saturday, November 17, 2012

Inversion Busting Winds

After diminishing for about 12 hours late Thursday night and Friday morning, winds picked back up Friday afternoon, and in spite of clear skies, winds overnight broke through the inversion, producing dramatic temperature swings in valley locations. Here's a high frequncyplot of temperatures from a suite of sensors near Smith Lake, off the west end of UAF West Ridge, showing a temperature rise of more than 10C in just a few minutes:

Courtesy UAF/IARC
Below is a plot of the hourly temperatures from Keystone Ridge, Goldstream Creek and Fairbanks Airport. Keystone Ridge, where winds have been northeast 15 to 30 mph since late Friday afternoon,  shows steady gradual cooling.The Goldstream Creek site shows, like Smith Lake, temperatures rising dramatically Friday evening, with gradual cooling since then. This well mixed boundary layer reflects the turbulent mixing produced by the winds. The situation at the Airport is more complex. The temperature did not pop-up until just before midnight, and a pool of cold air sloshed back over the airport between 5 and 7am. This cold pool is now being eroded away.


  1. Fascinating, thanks! I find it remarkable that the 8-m temperature remained higher than the 1-2 m temperature throughout, showing that despite mixing down the warmer air from above, there is still an inversion near the ground. I suppose that is just because an inversion is a stable equilibrium... it would take very strong winds or some radiative heating to break it up?

    It's amazing that during the rapid warming, the 8-m temperature was almost 10 C higher than the 1-m temperature. That's quite the sharp gradient!

    Glad you were able to return to blogging after the emergency trip - I hope all is well now.

  2. Richard,

    The four meter wind speed did not get above 2.5m/s, not strong enough for the mechanical mixing to completely overcome the radiative cooling.