Snow Grain Size and Albedo Retrievals for a Snow Aging Event – a Case Study Comparing Different Radiative Transfer Models

Snow grain size (SGS) and albedo are important snow physical parameters, which characterizes the metamorphic state of snowpack on ground. Monitoring of these parameters using remote sensing techniques may help to ascertain the cause/sources for reduction in albedo of snow over in-accessible regions. It is further linked to observed changes in melt rates of snow and also useful input for operational avalanche forecasters. In present work, reflectance information of snow in different spectral bands was used to retrieve the SGS and albedo values using radiative transfer (RT) models. An attempt was made to comprehend how different RT retrieval models capture the variation in actual snow physical parameters with the help of field data. Further, investigations were carried out to find RT model suitable for area under analysis. To achieve this, a comparative analysis of four different RT models was carried out using field spectral data of snow (with same history). Mono Spectral method was found to have higher sensitivity towards variation in SGS. Bi-Spectral method captured the essence of field measured conventional SGS values with higher accuracy (64.6%) than others (around 51%). Also, the coefficient of correlation between measured broadband albedo and simulated integrated albedo was found to be 0.82 with RMSD of 0.03.