An observational study of the surface-based radiation temperature inversion in Fairbanks, Alaska

Abstract

"Steep, surface-based inversions are a common occurrence in the valleys of interior Alaska due to the frequent occurrence of thermodynamically stable air masses caused in large part by the large negative net surface radiation balance present in high-latitude regions during wintertime. The inversion typically does not exceed heights of several hundred meters and can exhibit temperature ranges of up to 30°C from valley bottoms up to the top of the inversion. The main objective of this project was to improve the understanding of the surface-based inversion's temporal evolution by analyzing a suite of extra upper-air balloon launches released during clear and calm nights in Fairbanks. A series of radiosonde launches at high temporal frequency were conducted over seven case-study days spanning spring 2009 and fall/winter 2010. These case studies each present a unique story due to variability with respect to the effects of incoming solar radiation, snow cover, and winds on the development of the surface-based inversion. Several generalizations emerged which provided insight into the development of the surface based inversion with respect to these variables. In general, the surface temperature decreased most rapidly just after sunset. After this initial cooling pulse at the surface the profile begins to cool vertically. Another feature that appeared on several launches was when surface cooling appeared to cease, suggesting that some sort of temperature minimum had been attained. Cases without snow on the ground had larger surface temperature changes than those with snow cover. The presence of snow cover limits the diurnal surface temperature drop due to reflectivity of radiation which would heat up the surface during the day. This unique data set of two to three hour radiosonde launches could be the basis of future projects in air quality studies, modeling studies, and micrometeorological studies"--Leaf iii