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Title: SPATIAL PATTERNS IN SURFACE ENERGY BALANCE COMPONENTS DERIVED FROM REMOTELY SENSED DATA

Author
item HUMES, KAREN - UNIVERSITY OF OKLAHOMA
item HARDY, RAY - UNIVERSITY OF OKLAHOMA
item Kustas, William - Bill

Submitted to: Journal of the Professional Geographer
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: The spatial distribution in evapotranspiration across a watershed is critical in gaining an understanding of the interaction between terrestrial ecosystems and climate. Remotely sensing data can provide spatially distributed information on a number of key land surface characteristics and state variables which control evapotranspiration. When satellite data are combined with some near-surface meteorological measurements and a relatively simple model, spatial "maps" of evapotranspiration can be produced. Such an analyses from two watersheds with different characteristics is presented. The first is from a semi-arid grass and shrub ecosystem in Southern Arizona. Values of evapotranspiration varied considerably over the watershed studied and display a pattern similar to that of the cumulative precipitation in the area for at least 1-8 days prior to the image acquisition. The second set of examples are from central Oklahoma, which is in a semi-humid environment and includes a typical mix of cropland, short-grass prairie and woodlands. The spatial patterns in the variability of evapotranspiration observed over this watershed are influenced by both the cumulative precipitation just prior to image acquisition and the land cover type, with the precipitation amount being the dominant influence. This potential product using remote sensing technology will be essential for reliable monitoring of global climate change, accurate weather forecasting, and obtaining reliable regional crop growth and yield assessments.

Technical Abstract: Knowledge of the spatial distribution in energy balance across a watershed is a very important step toward gaining a better understanding of the exchanges and feedbacks of heat and moisture between the land surface and the lower atmosphere. Remotely sensing data can provide spatially distributed information on a number of key land surface characteristics and dstate variables which control the surface energy balance. When combined with some near-surface meteorological measurements and a relatively simple model, satellite data can be used to create spatially distributed "maps" of energy balance components over a watershed. In this paper, we present such analyses from two watersheds with different characteristics. The first is from a semi-arid grass and shrub ecosystem in Southern Arizona, utilizing ground and remotely sensed data from the MONSOON '90 experiments. Values of sensible heat flux varied considerably over the watershed studied and display a pattern similar to that of the cumulative precipitation in the area for at least 1-8 days prior to the image acquisition. The second set of examples are from central Oklahoma, which is in a semi-humid environment and includes a typical mix of cropland, short-grass prairie and woodlands. The spatial patterns in the variability of the sensible and latent heat fluxes observed over this watershed are influenced by both the cumulative precipitation just prior to image acquisition and the land cover type, with the precipitation amount being the dominant influence. Further work and other data sets will be required to examine the relative importance of precipitation amounts and land surface characteristics during more prolonged drying periods.