Analysis of cold airmass temperature modification across the US Great Plains as a consequence of snow depth and albedo

The presence of snow cover has been shown to modify atmospheric conditions through much of the earth's troposphere due to its radiative effects. Snow cover has garnered much attention in recent decades as a result of concerns associated with potential changes in the global environment that may be in tensified by the presence or absence of a snow cover. As a result, a greate r emphasis has been placed on the representation of snow cover in weather a nd climate prediction models. This study investigates the effects of snow a lbedo and snow depth on the modification of surface air temperatures within cold air masses moving across the U.S. Great Plains in winter Through the adaptation of a one-dimensional snowpack model, the thermal cha racteristics bf the core of a cold air mass were derived from the equation governing the heat balance between the surface and the lower atmosphere. Th e methodology was based on the premise that the core of a:cold air, mass ma y be considered homogeneous and not subject to advection of air from outsid e, thereby isolating the exchange of energy between the surface and the atm osphere as the control on lower-tropospheric temperatures. The adapted mode l included the synergism of the air mass-snow cover relationship through ti me, incorporating the natural feedback process. Simulation of surface air temperatures within four cold air masses over sno w cover of different albedo values and depths led to several conclusions. T n testing the effects of snow albedo, results indicate 1) mean daytime air temperatures 3 degrees-6 degrees C higher and maximum daytime air temperatu res 7 degrees-12 degrees C higher over snow with an albedo equal to 0.50 co mpared to 0.90, as a consequence of differences in sensible heat flux, and ultimately, absorbed solar radiation, and 2) little thermal inertia and the refore little difference in subsequent nighttime airmass temperatures over snow with an albedo of 0.50 compared to 0.90. In testing the effects of sno w depth, results indicate 1) little difference in daytime air temperatures associated with a snow depth of 2.5 cm compared to 15.0 or 30.0 cm, 2) an i ncrease in mean nighttime temperatures of 0.2 degrees-0.7 degrees C over a snow depth of 2.5 cm compared to either of the larger depths, and 3) a mask ing of the underlying bare soil surfaces: by the snow depths of 15.0 and 30 .0 cm and virtually no difference in airmass temperatures: over the two sno w depths. The potential utility of the results of this study lies in their applicatio n as additional guidance for temperature forecasts within wintertime cold a ir masses over, and downstream from, snow cover across the U.S. Great Plain s. Likewise, this study illustrates the importance of the various component s of the heat balance between the lower atmosphere and snow cover as based on the physical characteristics of the snowpack; which could prove benefici al in considerations of snow cover in weather and climate models.