GIS-based modelling of spatial pattern of snow cover duration in an alpinearea

Snow cover duration patterns of an alpine hillslope (approximately 2 km(2)) were derived using daily terrestrial photographic remote sensing. We have developed a suite of quantitative models in order to investigate the relati ve controls of topographic factors, the degree of non-linearity, the effect of seasonal differences and a possible influence of further systematic inf luences. We have only used data that are relatively easily available to ens ure applicability beyond the site. Elevation, slope angle and aspect, and p otential irradiation for the winter period can be directly derived from a d igital elevation model. The number of days with temperature less than or eq ual to0 degreesC was included using a regression with elevation. Furthermor e, a coarse vegetation classification (forested/not forested) was included. To estimate the necessary degree of non-linearity for such modelling witho ut forming exact assumption about the functional interrelations, results fr om a linear regression analysis are compared with an artificial neural netw ork (ANN). The results show that a R-2 of 71% can be achieved by means of a linear approach, whereas a non-linear approach (ANN) leads to 81%. An indi rect estimation demonstrates that a further 6%, can be explained without co nsidering data on annually specific weather conditions. The analysis of the residuals shows a clear spatial pattern. This indicates that additional sp atial variables may allow a further improvement of the model. (C) 2001 Else vier Science B.V. All rights reserved.