Handout (50.6 MB)
The goal of this work is to understand how snow processes are represented by NOAA’s National Water Model and its underlying land surface model, Noah MP, through a process-based study focused in California. Through a comparison with a network of snow pillows, we demonstrate that, when forced by NLDAS, the NWM underestimates snow water equivalent (SWE) systematically across the Sierra Nevada. This result is reinforced through a comparison in the Tuolumne River basin (TRB) using Airborne Snow Observatory SWE estimates, which finds large underestimates in NWM SWE at the highest elevations of the basin. The reasons for this underestimation are then explored with an idealized single-column Noah-MP simulation at a location in the TRB with very high-quality, long-term observations. Some differences in SWE accumulation and melt are understandable through comparison of differences between observed and NLDAS forcing, while other differences are harder to explain and suggest more systematic model deficiencies.
The outcome of this study will guide future improvements in NWM forcings and NWM physical processes inside the land surface model, and to develop snow data-assimilation techniques to potentially improve NWM prediction.
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