Estimating Potential Direct Insolation to Alpine Terrain

TitleEstimating Potential Direct Insolation to Alpine Terrain
Publication TypeJournal Article
Year of Publication1983
AuthorsIsard SA
JournalArctic and Alpine Research
ISBN Number0004-0851

This paper presents and evaluates two methods of estimating the potential for direct insolation to alpine terrain. A computer algorithm facilitates computation of integrated direct insolation receipts at variable spatial scales. Extensive mountain shadowing decreases the accuracy of insolation computations requiring small temporal and spatial scales of analysis. Simulations indicate that the variability associated with daily insolation to Indian Peaks, Colorado Front Range, cirques and glaciers is large (standard deviations often exceed 100 ly d<sup>-1</sup>). Application of the insolation model to Indian Peaks cirque basins confirms that incidence of direct solar radiation is strongly influenced by cirque aspect and time of year. However, the effects of the process controls are not strictly additive. The progression of the seasons has a more pronounced effect on daily insolation to north-facing cirques than to those oriented east or south. Computer simulations provide a basis for calibrating empirical equations (equinox and both solstices) that can be used to estimate potential direct insolation to rugged alpine terrain. Ground slope, aspect, and an obstruction index can be easily abstracted from topographic maps and used to estimate the spatial variability of insolation reduction within the Indian Peaks.