Spatial statistics of snowmelt

The physical processes that govern meltwater flow through snow are complex and spatially variable. Remote sensing studies may be a cost-effective approach for studying these variations, and may help to scale the knowledge obtained from field-scale observations and experiments. This paper focuses on the analysis of spatial variability of reflectance obtained from infrared photographs of a snow surface. Geostatistical techniques are used to extract meaningful parameters, such as correlation range and orientation of anisotropy, that may eventually give insight into the basic governing processes of snowmelt. 2.2 Reflectance images Aerial photographs of snow-covered areas were taken using 70-mm Kodak Infrared Aerographic type 2424 film. Visible light sensitivity was attenuated with a yellow filter (Wratten No.12). Infrared film was used because snow reflectivity is sensitive in that spectral range (Nolin & Dozier, 1993). The aerial photographs were digitized to produce reflectance images. Each pixel of the digitized image has a value in the range of 0 to 255 that represents the relative reflectance of infrared light. Adsorptive materials, such as rocks, appear as low values, while reflective material, such as snow, have higher values. A site-average scale factor of 570 mm per pixel was determined by mapping the distance between recognizable features in the photographs. A sample image is shown in Figure 1. This image was selected because of the large continuous snowcovered areas and the high contrast in those areas. The extent of the image is approximately 290 m by 280 m. 0 50 100 150 200 250