Snow Model for AWiFS Derived Broad Band Albedo with an Application to Onset Seasonal Melt in North-West Himalaya

Abstract

Albedo is a critical snow physical parameter that affects the earth’s climate system directly by altering the energy balance at the ground surface and indirectly by controlling the ecosystem processes. Thus spatial variability of snow albedo has immense importance in the study of geomorphology, climate dynamics, seasonal snow melt and hydrology. This paper describes and examines the retrieval of snow albedo for the period October 2012 to May 2013 by using multispectral Advance Wide Field Sensor (AWiFS) on board IRS-P6 of RESOURCESAT-1. The analysis procedure to compute spectral reflectance is achieved by converting the digital numbers after an image based atmospheric and topographic correction that include dark object subtraction (DOS) and effect of Rayleigh scattering on the transmissivity in different spectral bands of AWiFS images. Snow spectral reflectance and satellite derived snow albedo has been validated with in-situ data at the time of satellite pass over the study area using spectroradiometer, pyronometer and Automated Weather Station (AWS) respectively. A fine agreement between satellite derived snow albedo and in-situ measurements shows the relative accuracy of model. Present study also reveal the temporal and spatial variability of snow albedo in a basin which is an evidently indication of the seasonal melt due to decreasing trend in snow depth, snow cover area (SCA) and increased degree day temperature.