Tuesday, January 20, 2015

More on Warmth Aloft

Recently there's been much attention given to the fact that - according to the National Climatic Data Center - 2014 was the warmest year on record in Alaska.  This verdict is based on surface station measurements, but is also consistent with record warmth aloft as observed by balloon soundings.  For instance, we can look at the 1000-500 mb thickness, which is an excellent measure of the average temperature of the lower half of the atmosphere; we find that the 2014 mean 1000-500 mb thickness was higher than in any other year (1948-present) in Fairbanks, Barrow, and Kotzebue.  The thickness was second only to 1957 in Nome, McGrath, Bethel, and Anchorage.

One question that arose in my mind when pondering these new records was whether there were any 365-day periods in the past that were warmer than the calendar year 2014; after all, calendar year boundaries are artificial, like week or month boundaries throughout the year.  So I calculated the running 365-day mean 1000-500 mb thickness in Fairbanks and found that - remarkably - the highest values on record occurred in the past week.  Here's a list of the top several 365-day means with data complete through today (January 20); the top 61 overlapping periods ended in 2014 or 2015, and next in line was the year ending February 7, 1994.

Jan 17, 2014 - Jan 16, 2015   5344.20 m
Jan 18, 2014 - Jan 17, 2015   5344.15 m
Jan 16, 2014 - Jan 15, 2015   5343.83 m
Jan 19, 2014 - Jan 18, 2015   5343.63 m
Jan 20, 2014 - Jan 19, 2015   5343.62 m
Jan 21, 2014 - Jan 20, 2015   5343.44 m
Jan 15, 2014 - Jan 14, 2015   5343.23 m
May 21, 2013 - May 20, 2014   5343.03 m
Feb 8, 1993 - Feb 7, 1994   5338.53 m

Below is a chart of the running means since 1949.  The new record obviously reflects the remarkable combination of persistent unusual warmth and an absence of unusual cold; the last really notable cold spell (compared to normal) in Fairbanks was the exceptionally cold spring of 2013.


  1. That graph really mimics the corresponding temperature graph closely. You can really tell when there's been a positive PDO. But I guess this shouldn't be surprising since the southerly convection of warm air would pile in making the atmosphere thicker.

  2. Eric, yes indeed. The thickness is directly proportional to the mean temperature in the layer. It's a fabulous measure of lower atmospheric temperature trends.