A high-resolution distributed snowmelt model in an alpine catchment

TitleA high-resolution distributed snowmelt model in an alpine catchment
Publication TypeConference Proceedings
Year of Conference2000
AuthorsColee, M. T., Painter T. H., Rosenthal W., and Dozier J. C.
Conference Name68th Annual Western Snow Conference
Series TitleProceedings of the 68th Annual Western Snow Conference
Date PublishedApril 2000
PublisherWestern Snow Conference
Conference LocationPort Angeles, Washington
KeywordsModel, Snowmelt, Spatially distributed model

We run a physically based snowmelt model (SNTHERM.89) for each 30 m pixel in the Tokopah Valley, an alpine catchment in the Sierra Nevada of California. We use extensive field surveys to initialize and validate the distributed model (MrSNTHERM). We initialize with an April 1997 survey, as close to maximum snow accumulation as possible, and then compare the model results to a second survey in May 1997. Spatially distributed depth and density measurements were collected along a grid during these field surveys, and we use them to interpolate the initial snow surface. We derive initial snow-covered area (SCA) from Thematic Mapper (TM) data and albedo and surface grain size from Airborne Visible Infrared Imaging Spectrometer (A VIRIS) data. Meteorological data at hourly time steps from three stations within the basin are distributed over the basin based on observed lapse rates. Hourly solar radiation inputs to the model are calculated with the topographically corrected clear-sky radiation model TOPORAD and adjusted for cloud cover based on measured solar radiation from twosites in the basin. Hourly incoming longwave radiation is calculated from distributed temperature and relative humidity surfaces and is validated with measurements at two of the three meteorological stations. We evaluate model performance by comparing its outputs with the May field measurements of depth and density, AVIRIS derived snow cover and grain size, and TM-derived snow cover. To assess the accuracy of the model's snowmelt calculation, we compare them to measured basin hydrographs in two sub-basins as well as the entire basin.