Using weather balloon launches to understand the Fairbanks surface-based temperature inversion lifecycle

Steep, surface-based inversions are a common occurrence in the valleys of interior Alaska due to the highly stable air masses and the large negative surface radiation balance present in high-latitude regions during wintertime. The inversion typically does not exceed heights of several hundred feet and can encompass temperature gradients of up to 30˚C. These strong inversions effectively trap particulates from biomass and hydrocarbon burning near the surface, creating health risks for many residents in the Middle Tanana Valley. The timeliness and accuracy of air quality forecasts are increasingly important because of regional population growth and an upward trend in the use of woodstoves, caused by high oil prices. This in turn requires better understanding of the inversion lifecycle. By analyzing twice daily data from radiosondes launched at 00 UTC and 12 UTC one can understand the diurnal trend of inversion formation and dissipation during the spring and autumn seasons and come to general conclusions about the inversion's lifecycle. Because these observations are only taken once every twelve hours, the evolution of the inversion between these standard reporting periods is unknown. Our observational program, initiated in spring 2009, has used weather balloons to investigate how the surface-based temperature inversion evolves between the standard weather balloon launches, and to explain these patterns in terms of various physical and synoptic factors, such as wind, incoming solar radiation and sun angle. The spring and autumns seasons were chosen to analyze in this study since there is a defined diurnal effect in the evolution of the surface-based temperature inversion these times of year, unlike winter in interior Alaska when changes in the surface-based temperature inversion are dependent solely on synoptic pattern changes.