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Research Project: Spatial Snow Density Estimates in Support of ASO: Combining Ground Based Radar and In-Situ Measurements with Energy Balance Modeling

Location: Watershed Management Research

Project Number: 2052-13610-012-03-T
Project Type: Trust Fund Cooperative Agreement

Start Date: Aug 4, 2016
End Date: Jan 31, 2019

This project is a partnership between NASA/JPL and ARS Northwest Watershed Research Center snow modeling program. The ARS component is the third leg of the ASO stool – aircraft over flights, lidar and spectrometer data processing, and energy balance snow modeling. The first two are the responsibility of NASA/JPL, while the last – snow modeling – is the responsibility of ARS. While initially ARS provided only support for the NASA/JPL efforts in the form of snow density fields, ARS is now a full and equal partner in the ASO undertaking. Fundamental to this project, the ARS iSnobal model was designed for integration with remote sensing data, and is the ideal tool for evaluation of the ASO data products. Interaction between the model and the ASO lidar can include using the model to define the snow density in order to convert the lidar derived depths to SWE, and updating the model with ASO derived depth and SWE products. As the ASO program develops, the model will be forced with snow albedo derived from the ASO imaging spectrometer, and updated with ASO-lidar derived snow depth data. A manuscript Optimizing a high resolution snow redistribution model in sub alpine terrain using multi-temporal airborne lidar is being revised for publication in Journal of Hydrometeorology. This manuscript describes an early multi-temporal lidar snow depth assessment the NASA Cold Lands Processes Experiments (CLPX) of 2003-2007. In a February 2009 experiment conducted over the Reynolds Creek Experimental Watershed we evaluated concurrent lidar, ground-based Radar, field measurements and simulation modeling. Initial analyses indicate that lidar snow depth RMS uncertainty was 30 cm. The field campaign however revealed an approximate 10cm bias due to absolute GPS errors that when accounted for reduced snow depth uncertainties by one-third. The field campaigns and iSnobal modeling will aid in determining biases and defining and reducing uncertainty in the ASO-lidar retrievals.

In support of the NASA/JPL Airborne Snow Observatory (ASO) flight campaigns during Spring 2016, the USDA ARS Northwest Watershed Research Center will: 1. Perform iSnobal simulations over the Tuolumne basin in the Sierra Nevada, using the Spatial Modeling Resource Framework (SMRF) (developed for this project) to acquire station data, including current precipitation and meteorological data. 1.1 Snow density fields will be provided to ASO staff at within 24 hours of each LiDAR over-flight. 1.2 The number of model simulations will be dependent on the number of ASO flights in the Tuolumne 2. Integrate ASO LiDAR snow depths into iSnobal model data stream; 2.1 Re-run simulations from 2013 2015 using SMRF and re-starts at ASO over flight dates with LiDAR snow depths integrated into iSnobal data stream providing ASO team with results. To satisfy ARS responsibilities in the ASO collaboration, to provide the snow and hydrologic modeling component of the NASA/JPL Airborne Snow Observatory flight campaigns Water Year 2017, the USDA ARS Northwest Watershed Research Center will deliver the following: 1. Real-time simulation of snow deposition and melt over the Tuolumne, including the Cherry and Eleanor sub-basins. These simulations will include updates of the model state for each ASO lidar over flight, reports on before and after update SWE volume and snow cover thermal state to be to be included as an additional product with the lidar-derived SWE. 2. Participate in field validation efforts, including Snow-X in Colorado. 3. Investigate an improved density algorithm of iSnobal.