Friday, October 18, 2013

Inversion Season is Here…Sans Snow

Nature provided a perfect laboratory on Tuesday on the role that decreasing solar heating plays in Interior Alaska climate this time of year. A warm airmass covers the Interior: clouds thinned out a bit Thursday morning, allowing for about a 10ºF inversion to develop on the valley floor. However, by sunrise thick cirrus returned, and then there was even a bit of rain, just a hundredth or two in most places, in the early afternoon. Combined with a lack of wind, and the results are seen in the upper air sounding from Thursday afternoon. While the inversion is boring for winter, it's occurrence without any snow to be found below 3000" elevation is quite telling.

This inversion is reflected in the high temperatures Thursday:
Fairbanks Upper Air: 45ºF
Goldstream Valley Bottom: 45ºF
Aurora: 47ºF
Fairbanks Airport: 48ºF
Fort Wainwright: 48ºF
Eielson AFB: 51ºF

But in the hills...
Stuart Creek RAWS: 58ºF
Gilmore Creek CRN: 56ºF
Keystone Ridge: 54ºF
Wichersham Dome: 52ºF
Clearly Summit: 51ºF

1 comment:

  1. Very nice, Rick. So snow cover is not the only way to get a significant surface-based inversion that survives the day. It is an interesting question as to how much of an inversion could be eradicated by even a completely sunny day at this time of year (no snow). With no wind, I suspect the solar input might be too small to create deep thermal mixing even with no snow. Today is a case in point: temperatures would have reached the low 60s if the boundary layer had become completely well mixed.