| Energy and moisture fluxes at the land-air interface are the lower boundary conditions of atmospheric circulation models (ACMs). They are strongly affected by the land cover, soil type, soil and canopy temperatures, and moisture content/state. Considerable effort has been made to improve the representations of these parameters as they are incorporated in ACMs. During the past two decades, this effort has included the use of remote sensing techniques to estimate surface moisture content and temperature. The goal of this thesis is to link the best of the one-dimensional, physically-based, hydrologic models to a radiobrightness signature for bare soil and for a prairie grassland. Versions of the one-dimensional Hydrologic (1dH) model estimate surface energy and moisture fluxes, and soil temperature and moisture content/state profiles for bare soil and prairie grassland. The linked hydrology/radiobrightness models (1dH/R) offer a means of validating the models through comparison with field data, and the possibility of correcting model-based estimates of system state through the assimilation of satellite data.; This study has two phases. The focus of the first phase is to develop the 1dH model for bare soils subject to insolation, radiant heating and cooling, and sensible and latent heat exchanges with the atmosphere. The soil is modeled as a freezing and thawing medium with its moisture and temperature governed by coupled partial differential equations. A finite difference scheme is employed to solve the governing equations for soil temperature and moisture content. The 1dH model is linked to a quasi-specular, microwave emission model for the bare soil.; The focus of the second phase is the addition of a grass canopy to the 1dH/R model. The grass is divided into two layers, a canopy layer that is treated as a biophysical medium with dynamic energy and moisture exchanges with the soil and atmosphere, and an insulating layer of thatch that is modeled as a medium subject to radiation exchange with the canopy and underlying soil. A mixed index of refraction concept is used to estimate radiobrightness. Predictions from the 1dH/R model are compared with observations from our Radiobrightness Energy Balance Experiment (REBEX-1) on prairie grassland near Sioux Falls, South Dakota, during the fall and winter of 1992-1993. |
