High-resolution Land Surface Modeling and Data Assimilation

A 51-year simulation of water and energy fluxes over the entire Arkansas-Red based was performed using a fully distributed land surface model. The simulations were performed at fine temporal (hourly) and spatial (1 squ. km) resolutions in an effort to bridge the gap between traditional hydrologic modeling, typically at final temporal spatial resolutions on relatively small catchment, and regional land surface modeling. Our approach in model validation is to focus on both the accuracy of streamflow simulations at the sub-basin scale and appropriate physically based description of heat and water exchange at the land surface-atmosphere interface because biases at the sub-basin scale may grow nonlinearly over time and lead to larger basin-scale biases. Preliminary analysis of the simulations shows that the spatial patterns of temporarily averaged water balance components are similar to published climatological patterns and clearly illustrates the strong east-west gradients of precipitation, runoff, and evapotranspiration. Streamflow accumulations at the sub-basin scale show good agreement betweens simulated and observed streamflow for catchments ranging in size between 880 km2 and 4211 km2. Results of energy flux simulations shown in this study are in reasonable agreement with observations. Analysis of the spatial distribution of precipitation and runoff highlights the similarities and differences between the two. The relationship between precipitation anomalies and runoff and soil water storage anomalies was examined. The study is ongoing and more validation at the sub-basin scale is being done. We hope that the results of this analysis will help clarify the sources of long-term hydrologic variability within the basin.