Coarse spatial resolution satellite remote sensing of drought conditions in Nebraska: 1987-1988

Neither the Palmer Drought Severity Index (PDSI) nor the Crop Moisture Index (CMI) allow for detection of the onset, spatial extent, severity, and termination of drought. The dearth of sampling stations, the generally irregular geographic pattern of these data-collection sites, and certain inherent time-lag factors all combine to reduce the practical utility of both the PDSI and CMI. Therefore, the purpose of the research was to evaluate satellite remote sensing with systems of coarse spatial resolution as a potential tool for detecting and monitoring drought conditions in Nebraska. Twenty-two datasets acquired by the NOAA Advanced Very High Resolution Radiometer (AVHRR) during 1987 and 1988 were transformed to Normalized Difference Vegetation Indices (NDVI). Analyses focused on individual crop-reporting districts in Nebraska. Digital processing was accomplished with hardware systems and software packages which are available commercially. Results of the research included a better temporal correlation between average NDVI and CMI than between NDVI and PDSI, seasonal NDVI curves that were free of radiometric errors, good correlations between seasonal NDVI and precipitation, and evidence that the NDVI transformation is less useful in semi-arid Western Nebraska than in more humid portions of the state. Analysis of seasonal NDVI measurements allowed correct identification of the geographic core of the 1988 drought in Nebraska. The necessity of real-time acquisition of AVHRR data for an operational drought-monitoring system is highlighted