Application of remote sensing techniques to measurement of windblown dust over the Columbia Plateau.

摘要

The Columbia Plateau PM₁₀ Project (CP3) is a multidisciplinary program to investigate the effect of windblown dust upon air quality within the Columbia Plateau of eastern Washington, northeastern Oregon and northern Idaho. The research presented here involves three applications of spectral remote sensing technologies in support of CP3 objectives to characterize regional vegetative cover and to determine aerosol dust burdens in the atmosphere. In the first application, data from the Advanced Very-High Resolution Radiometer (AVHRR) were used to construct a detailed vegetation map for input to an air quality modeling system for windblown dust. Composite biweekly AVHRR data were used in conjunction with soils maps to develop vegetation classes (including conservation lands), defined by modeling requirements, through a spectral clustering technique. The vegetation map was validated using both ground-truth observations and NDVI (normalized difference vegetative index) results from the entire growing season, and at multiple locations. The result is a validated vegetation map meeting the requirements of the CP3 air quality modeling system. In the second application, ground-based Multi-filter Shadow-band Radiometer (MFRSR) measurements collected at two sites were used to determine the aerosol optical thickness (AOT) through the 1998 growing season and including an April, 1998 Asian dust influx. The AOT reached a maximum of ∼0.45 at 500 nm during the Asian dust event. Finally, the third application employed a contrast method to obtain AOT from two pairs of AVHRR images; results were evaluated using MFRSR-derived AOT observations. The method yielded reasonable results in one case (∼0.14 compared to MFRSR AOT of 0.07) and inconclusive results in the other. This experiment was the first application of the contrast method for AOT from AVHRR imagery to a mid-latitude continental region and represents progress toward an observationally based continental dust climatology. Taken together, these three applications demonstrate the promising potential of these radiometric remote sensing techniques for providing data for measurement and modeling of the dust aerosol in an arid midlatitude continental region.