DROUGHTS OF THE LATE 1980S IN THE UNITED-STATES AS DERIVED FROM NOAA POLAR-ORBITING SATELLITE DATA

Drought is one of the most adverse and powerful weather-related disast ers that occur every year across a portion of the United States. The c onsequences of droughts quite often can be devastating. To mitigate th ese consequences, droughts require careful monitoring. Recently, NOAA' s National Environmental Satellite Data and Information Service develo ped a new Advanced Very High Resolution Radiometer-based vegetation co ndition index (VCl) that showed good results when it was used for drou ght detection and tracking. The VCl is a vegetation index with reduced noise and is adjusted for land climate, ecology, and weather conditio ns. This index provides a quantitative estimate of weather impact on v egetation and also measures vegetation conditions. Several large-area experiments showed that the VCl had excellent ability to detect drough t and to measure the time of its onset and its intensity, duration, an d impact on vegetation. The VCl provides accurate drought information not only for the cases with well-defined, prolonged, widespread, and v ery strong droughts, but also for very localized, short-term, and ill- defined droughts. The advantages of this index compared to conventiona l ground data are in providing more comprehensive, timely, and accurat e drought information. This paper describes the methodology and techni cal principles used to derive the vegetation condition index, explores data processing, and gives many examples of VCl application for droug ht monitoring in the United States during 1985-90. The spatial and tem poral patterns of VCl-derived drought were in a very good agreement wi th the identical patterns identified from precipitation and yield anom alies.