Date of Completion
Guiling Wang, Mekonnen Gebremichael
Field of Study
Master of Science
Soil moisture is a key water cycle parameter, known to have a positive feedback on precipitation, namely, an increase in soil moisture would increase net radiation and latent heat flux and decrease sensible heat flux and consequentially lower the boundary layer height and increase moist static energy, which eventually leads to precipitation increase. Arguably, land surface models that simulate land surface processes and the surface fluxes to the atmosphere do not capture adequately the spatial variability of soil moisture, particularly over land surface areas with complex topography. A parameterization is applied in this study to the Community Land Model (CLM) 3.5 in an effort to correct for the spatial bias of soil moisture and understand the consequential effects on the simulated water cycle parameters. This parameterization includes a groundwater recharge term from surface water. While CLM contains a river transport model to close the water budget, its current version neglects this groundwater re-infiltration term. Using satellite soil moisture data over the Blue Nile basin, this parameterized term is shown to have a positive correlation to contributing area, which is defined at each grid cell and represents the number of grid cells whose surface drainage accumulates at that local grid cell. With the new parameterization applied to CLM, soil moisture, soil temperature, evapotranspiration flux, water table depth, and vegetation water content all showed significant differences from the control CLM run (without the parameterization) at 95% confidence level. The differences in the spatial distribution of these variables are expected to affect precipitation simulations from regional climate modeling. As Ethiopia is a region that has one of the greatest inter-annual and seasonal precipitation variability globally, the ability to forecast long-term and regional climate predictions is essential. This would allow for optimal reservoir operations including buffering of water resources during times of drought.
Wu, Di, "Improving the Surface-Ground Water Interactions in the Community Land Model: Case Study in the Blue Nile Basin" (2013). Master's Theses. 476.
Emmanouil N. Anagnostou