Evaluating the Suitability of NLDAS-2 Climate Data for Watershed Modeling: A Case Study of AnnAGNPS in Goodwin Creek Experimental Watershed in Mississippi

This study evaluates the suitability of the North American Land Data Assimilation System Phase 2 (NLDAS-2) gridded climate dataset as a substitute for in situ climate observations in the context of watershed modeling with the Annualized Agricultural Non-Point Source (AnnAGNPS) watershed model. NLDAS-2 offers continuous and long-term climate data, including precipitation, temperature, humidity, wind, solar radiation, and potential evapotranspiration. The study focuses on the Goodwin Creek Experimental Watershed (21.3 km2) in north Mississippi from January 1982 to January 2002 as a test case. A sensitivity analysis of AnnAGNPS outputs in response to different sets of climate forcing scenarios followed by a comparison of AnnAGNPS simulations against field observations including runoff and sediment load in two locations were conducted. Results show that NLDAS-2 performed comparably to field-based inputs in this edge-case setting despite the coarser resolution of the NLDAS-2 grid compared with the watershed area. These findings support the use of NLDAS-2 for process-based watershed modeling in data-scarce or ungauged watersheds and highlight its value as a spatially and temporally continuous data product.