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United States Department of Agriculture

Agricultural Research Service

Research Project: Spatial Snow Density Estimates in Support of ASO:Combining Ground Based Radar with Energy Balance Modeling

Location: Northwest Watershed Management Research

2013 Annual Report


1a.Objectives (from AD-416):
In support of the NASA Airborne Snow Observatory (ASO) flight campaign in Colorado and California during Spring 2013, the USDA ARS Northwest Watershed Research Center and the Cryosphere Geophysics and Remote Sensing group at Boise State University propose to: 1.1 Perform initial iSnobal simulations over the Tuolumne basin in the Sierra Nevada, using precipitation and meteorological data. 1.2 Investigate modification of the density/depth functionality in the iSnobal snow model. 1.3 Develop procedures for precipitation and weather data ingestion to support “real-time” iSnobal simulations. 1.4 Develop procedures for actively reinitializing iSnobal simulations using ASO-LiDAR derived depths to support “real-time” iSnobal SWE prediction. 1.5 Quantify uncertainty and bias in both ASO-LiDAR and iSnobal simulated SWE using data from ground radar-derived SWE, and in-situ measurements of depth and density. 1.6 Use data collected and preliminary results to develop a multi-year proposal to use ground-based radar and airborne LiDAR observations to optimize iSnobal over the study region. A major emphasis will be placed on improving the model estimates of density to provide SWE estimates derived from a combination of LiDAR snow depths and iSnobal density estimates.


1b.Approach (from AD-416):
Use the iSnobal energy balance snow model first to inform the design of the field campaigns, then to obtain spatially distributed snow densities to accurately convert ASO depth data to SWE products. iSnobal simulations will be used to estimate density to combine with LiDAR-derived snow depths for estimates of SWE volume over each study area. These initial simulations will then be updated using a combination of the radar SWE estimates and the in-situ measurements from the field campaigns. Improvement of the iSnobal density function will be undertaken following the 2013 field campaign, for updating the SWE volume estimates, and determination of an overall uncertainty distribution, based on LiDAR, simulation model and GPS errors, over the Sierra field site.


3.Progress Report:

This is the final report for agreement 5362-13610-010-06T terminated on July 31, 2013. In FY2013, ARS modeling expertise was applied to supply the Airborne Snow Observatory (ASO) group with snow and energy balance data. Prior to the ASO airborne campaign, maps of solar loadings were delivered to help determine field sampling locations. Preparation of the Isnobal snow and melt model for near real-time simulations was carried out in March. Set-up included the creation of automated scripts and programs to retrieve meteorological observations from eight sites, to spatially distribute these data to generate model forcings, and to ultimately run and administer the Tuolumne snow modeling simulations and outputs. The snow model was set up and run in near real-time for the ASO-selected Tuolumne River Basin upstream of Hetch Hetchy Reservoir, California, on an as-needed basis from mid-April through early June. Simulated Snow Water Equivalent and density distributions were electronically transferred to ASO on seven occasions during this timeframe. Analysis of the 2013 work will continue through FY2013. This agreement was established in support of objective 3 of the in-house project, the goal being to expand integrated snow hydrology modeling to larger scales, coupling to belowground processes, including wind effects on precipitation input, and helping to incorporate snow-related processes into ARS watershed and management simulation models (e.g., SWAT, AnnAgNPS, KINEROS, AgES, AGWA, RHEM, ISNOBAL, PIHM, etc).


Last Modified: 10/1/2014
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