Drought detection and quantification by reflectance and thermal responses
1983
Wiegand, C.L. | Nixon, P.R. | Jackson, R.D.
Drought can be detected by its effect on plant canopy development as indicated by measurements of biomass production, leaf area index (LAI), and ground cover in the reflective wavelengths (0.4–2.5 μm) and by canopy minus air temperature in the thermal infrared (8–14 μm) wavelengths. Both measures are quantitative, but quantification in terms of drought's economic impact requires that relationships between canopy ‘appearance’ as revealed by the measurements and effect on salable plant parts be established. The measurements themselves are becoming routine and their quantification in terms of drought's economic impact on grain sorghum and wheat grain yields have been demonstrated, but are not yet routine. Seven considerations in a system for drought quantification are discussed, and results of semi-operational applications to drought assessment that incorporate most of the seven considerations are described. Future drought assessment systems will likely combine physiologically based crop growth and yield models with soil characteristics, weather data, and Earth satellite spectral scanner observations.
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