Tuesday, February 25, 2014

Near-Record Inversion

The temperature inversion above Fairbanks reached near-record strength yesterday morning, with a temperature difference of more than 30 °C between the surface and the warmest level aloft.  This has been observed only three times before in February, on three consecutive days in 1989.  The February record for strongest inversion (from the surface to the warmest level aloft) is 32.9 °C.

While we're on the topic of upper-air temperatures, I created a graphic to visualize the evolution of temperatures aloft through the winter thus far - see below.  This is a time-height cross-section of the balloon sounding temperatures at Fairbanks; the freezing line is denoted with a black contour.  The remarkable warmth in October and January is readily apparent, as is the relative scarcity of deep cold air.  Of course this graphic might be more useful if it showed temperature anomaly rather than actual temperature, but it will take a bit more work to develop the daily climatology at each level.


  1. Is the cutoff at the bottom due to geopotential height? If so, would it be too much to put the y-axis in feet? That means more to casual observers.

    If you really want to do work: take a north-south slice (crossing Fairbanks) height profile across the stretch of Alaska maybe using reanalysis data. That would be cool. Over a few slides or animations you would see the progression of warm and cold air at the different latitudes and altitudes. Just putting that out there.

    1. Eric,

      Yes, the bottom cut-off in the data is simply the surface, where the pressure varies. I would gladly plot the data against altitude, except that the height values are missing for most of the levels in the data set I am using (from NCDC). The top of the chart, at 800 mb, is around 5500-6500 feet but varies considerably of course.

    2. Well if anything it makes for an interesting observation. Usually it is taken that winter high pressure means clear skies and thus colder temps. But the graph says it doesn't really matter as much. Temps will increase or decrease regardless of the surface pressure.

  2. I really like the time-height cross-section graphic. Great job.