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An examination of land surface -atmosphere interactions in the Nebraska Sand Hills

David B Radell, University of Nebraska - Lincoln

Abstract

The Sand Hills of Nebraska are a unique physiographical entity, consisting of grass stabilized sand dunes with shallow vegetation-covered valleys composing the inter-dunal valley areas. The wettest valleys have a net upward gradient of soil moisture, moist soils and plentiful vegetation while the sand dunes have very dry soils and limited vegetation cover. These distinct differences in the land surface and their resulting impact on the atmosphere are investigated in this dissertation. Meteorological observations from three contrasting environments with varying influence of the water table in the Nebraska Sand Hills were studied to document the changes in the components of the surface energy budget over various time scales. It was determined that significant differences in the partitioning of the surface energy budget existed among the sites resulting from differences in land surface characteristics. An uncoupled land surface model, forced with observations from each site, was then used to test its ability to reproduce those surface energy budget differences. The model was able to reasonably reproduce the surface energy budget at locations where subsurface water was not a major influence, but displayed difficulty in capturing the influence of a high water table at one inter-dunal valley location. A source of subsurface water was then added to the land surface model to account for the additional contribution to the soil moisture profile as documented from an inter-dunal valley Sand Hills' site. It was concluded that, with the addition of the monthly varying water table, the root zone soil moisture profile was better modeled and resulted in more accurate estimates of the surface energy budget and evapotranspiration. Through use of the land surface model coupled to a two-dimensional numerical weather prediction model, the influence of two soil moisture regimes representing the Sand Hills' inter-dunal valleys on idealized deep moist convection was also investigated. Results indicate that the soil moisture plays a secondary but important role in the pre- and developing squall line environment. ^

Subject Area

Atmospheric Sciences

Recommended Citation

Radell, David B, "An examination of land surface -atmosphere interactions in the Nebraska Sand Hills" (2007). ETD collection for University of Nebraska - Lincoln. AAI3284241.
http://digitalcommons.unl.edu/dissertations/AAI3284241

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