A land surface process/radiobrightness model with coupled heat and moisture transport for prairie grassland

• Published in: IEEE transactions on geoscience and remote sensing Vol. 37; no. 4; pp. 1848 - 1859
• Main Authors: Yuei-An Liou, Galantowicz, J.F., England, A.W.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.07.1999; Institute of Electrical and Electronics Engineers
• Subjects: Applied geophysics; Atmospheric modeling; Brightness; Canopies; Computer simulation; Cooling; Density; Earth sciences; Earth, ocean, space; Error analysis; Exact sciences and technology; Grasslands; Heat radiation; Hydrology; Internal geophysics; L-band; Land surface; Mathematical models; Microwaves; Modules; Moisture; Precipitation (meteorology); Predictive models; Soil; Soil (material); Soils; Solar heating; Surficial geology; Temperature; Variance; Vegetation; microwaves; atmospheric precipitation; simulation; Space remote sensing; vegetation; transport; brightness; grasslands; one-dimensional models; temperature; humidity; soils; heat transfer; errors; radiance
• ISSN: 0196-2892
• DOI: 10.1109/36.774698

The authors present a biophysically based, one-dimensional hydrology/radiobrightness (1dWR) model for prairie grassland that is subject to solar heating, radiant heating and cooling, precipitation, and sensible and latent heat exchanges with the atmosphere. The 1dH/R model consists of two modules, a one-dimensional hydrology (1dH) module that estimates the temperature and moisture profiles of the soil and the canopy and a microwave emission module that predicts radiobrightness (R). The authors validate the 1dH/R model by comparing its predictions with data from a field experiment. The model was forced by meteorological and sky radiance data from their Radiobrightness Energy Balance Experiment (REBEX-1) on prairie grassland near Sioux Falls, SD, during the fall and winter of 1992-1993. Model predictions were compared with 995 consecutive REBEX-1 observations over a 14-day period in October. Average errors (predicted-measured) for canopy temperature are 1.1 K with a variance of 3.72 K/sup 2/, for soil temperatures at 2-, 4-, 8-, 16-, 32-, and 64-cm depths are 2 K with a variance of 4 K/sup 2/, and for H-polarized brightnesses are 0.06 K with a variance of 1.30 K/sup 2/ at 19 GHz and 6.01 K with a variance of 6.04 K/sup 2/ at 37 GHz. The model overestimates the 37-GHz brightness because they have not included scatter darkening within the vegetation canopy in the model. They use the 1dH/R model to simulate a 60-day dry-down of prairie grassland in summer. For grass with a column density of 3.7 kg/m/sup 2/ and soil with an initially uniform moisture content of 38% by volume, the upper 5 mm of soil dries to 27% by the end of the simulation. The corresponding L-band brightness increases from an initial 143 K to a final 163 K. In contrast, none of the special sensor microwave/imager (SSM/I) radiobrightnesses nor the radiobrightness thermal inertia (RTI) technique, either at L-band or at any SSM/I frequency, exhibits significant sensitivity to the soil dry-down.