Comparative analysis of relationships between NLDAS-2 forcings and model outputs

This study reports results from an analysis of the relationship between atmospheric forcing and model-simulated water and energy fluxes for the North American Land Data Assimilation System Project Phase 2 (NLDAS-2). The relationships between mean monthly precipitation and total runoff are stronger in the Sacramento (SAC) and variable infiltration capacity (VIC) models, which grew out of the hydrological community, than in the Noah and Mosaic models, which grew out of the soil-vegetation-atmosphere transfer (SVAT) community. The reverse is true for the relationship between mean monthly precipitation and evapotranspiration. In addition, surface energy fluxes in VIC are less sensitive to model forcing (except for air temperature) than those in the Noah and Mosaic model. Notwithstanding these general conclusions, the relationships between forcings and model-simulated water and energy fluxes for all models vary for different seasons, variables, and regions. These findings will ultimately inspire a combination of SVAT-type model energy components with hydrological model water components to develop a SVAT-hydrology model to improve both evapotranspiration and total runoff simulations.