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Distributed assimilation of satellite‐based snow extent for improving simulated streamflow in mountainous, dense forests: An example over the DMIP2 western basins
Author(s) -
Yatheendradas Soni,
Lidard Christa D. Peters,
Koren Victor,
Cosgrove Brian A.,
De Goncalves Luis G. G.,
Smith Michael,
Geiger Jim,
Cui Zhengtao,
Borak Jordan,
Kumar Sujay V.,
Toll David L.,
Riggs George,
Mizukami Naoki
Publication year - 2012
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2011wr011347
Subject(s) - snowmelt , snow , streamflow , environmental science , data assimilation , evapotranspiration , moderate resolution imaging spectroradiometer , tree canopy , satellite , meteorology , climatology , hydrology (agriculture) , canopy , drainage basin , geology , geography , ecology , archaeology , aerospace engineering , engineering , biology , geotechnical engineering , cartography
Snow cover area affects snowmelt, soil moisture, evapotranspiration, and ultimately streamflow. For the Distributed Model Intercomparison Project – Phase 2 Western basins, we assimilate satellite‐based fractional snow cover area (fSCA) from the Moderate Resolution Imaging Spectroradiometer, or MODIS, into the National Weather Service (NWS) SNOW‐17 model. This model is coupled with the NWS Sacramento Heat Transfer (SAC‐HT) model inside the National Aeronautics and Space Administration's (NASA) Land Information System. SNOW‐17 computes fSCA from snow water equivalent (SWE) values using an areal depletion curve. Using a direct insertion, we assimilate fSCAs in two fully distributed ways: (1) we update the curve by attempting SWE preservation, and (2) we reconstruct SWEs using the curve. The preceding are refinements of an existing simple, conceptually guided NWS algorithm. Satellite fSCA over dense forests inadequately accounts for below‐canopy snow, degrading simulated streamflow upon assimilation during snowmelt. Accordingly, we implement a below‐canopy allowance during assimilation. This simplistic allowance and direct insertion are found to be inadequate for improving calibrated results, still degrading them as mentioned above. However, for streamflow volume for the uncalibrated runs, we obtain: (1) substantial to major improvements (64–81%) as a percentage of the control run residuals (or distance from observations), and (2) minor improvements (16–22%) as a percentage of observed values. We highlight the need for detailed representations of canopy‐snow optical radiative transfer processes in mountainous, dense forest regions if assimilation‐based improvements are to be seen in calibrated runs over these areas.