Impact of Real‐Time Satellite‐Derived Green Vegetation Fraction on National Water Model Fluxes in Humid Alabama Watersheds

Vegetation is parameterized in the operational National Oceanic and Atmospheric Administration National Water Model (NWM) using climatologies of leaf area index and green vegetation fraction (GVF) which do not capture interannual variability or seasonal anomalies. This study investigates the impact of assimilating real-time Visible Infrared Imaging Radiometer Suite (VIIRS) GVF on NWM streamflow and land surface energy and moisture fluxes. Using a subset of the NWM over three humid watersheds in Alabama, VIIRS GVF was assimilated into an experimental NWM configuration to replace the default GVF climatology to provide a more accurate representation of the land surface vegetation greenness. Although the use of real-time VIIRS GVF in place of the climatological GVF slightly improved NWM stream-flow prediction, results were not statistically significant. GVF assimilation also improved the interannual representation of land surface fluxes with increases in GVF resulting in increased evapotranspiration and latent heat.