Submitted to: Journal of Hydrometeorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2007
Publication Date: 10/1/2007
Citation: Sharif, H., Crow, W.T., Miller, N., Wood, E. 2007. Multi-decadal high-resolution hydrologic modeling of the Arkansas/Red River Basin. Journal of Hydrometeorology. 8(5):1111-1127. Interpretive Summary: The inability to properly represent fine-scale (< 10 km ) land surface heterogeneity in land surface models is a major source of error in model predictions that could otherwise enhance our ability to monitor root-zone soil moisture, evapotranspiration, and runoff in agricultural areas. The analysis describes some long-term land surface model simulations run by very high spatial resolution at considerable computational costs. These simulations help us understand the impact of - typically non-resolved - fine scale heterogeneity in land surface model outputs. The eventual goal is improved simulations at lower computational costs.
Technical Abstract: Land surface heterogeneity and its effects on surface processes have been a concern to hydrologists and climate scientists for the past several decades. The contrast between the fine spatial scales at which heterogeneity is significant (1km and finer) and the coarser scales at which most climate simulations with land surface models are generated (10s to 100s of kms) remains a challenge, especially when incorporating land surface and subsurface lateral fluxes of mass. In this study, long-term observational land surface forcings and derived solar radiation were used to force high-resolution land surface model simulations over the Arkansas/Red River basin in the Southern Great Plains region of the United States. The most unique aspect of these simulations is the fine space (1 km2) and time resolutions (hourly) within the model relative to the total simulation period (51 years) and domain size (575,000 km2). Runoff simulations were validated at the sub-basin scale (10 – 7,000 km2) and were found to be in good agreement with observed discharge from several unregulated sub-basins within the system. A hydroclimatological approach was used to assess simulated annual evapotranspiration for all sub-basins. Simulated evapotranspiration values at the sub-basin scale agree well with predictions from a simple one-parameter empirical model developed in this study according Budyko’s concept of “geographical zonality”. The empirical model was further extended to predict runoff and evapotranspiration sensitivity to precipitation variability and good agreement with computed statistics was also found. Both the empirical model and simulation results demonstrate that precipitation variability was amplified in the simulated runoff. The fine scale at which the study is performed allows analysis of various aspects of the hydrologic cycle in the system including general trends in precipitation, runoff, and evapotranspiration, their spatial distribution, and the relationship between precipitation anomalies and runoff and soil water storage anomalies