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- Author or Editor: Felix N. Kogan x
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Drought is one of the most adverse and powerful weather-related disasters that occur every year across a portion of the United States. The consequences of droughts quite often can be devastating. To mitigate these consequences, droughts require careful monitoring. Recently, NOAA's National Environmental Satellite Data and Information Service developed a new Advanced Very High Resolution Radiometer–based vegetation condition index (VCI) that showed good results when it was used for drought detection and tracking. The VCI is a vegetation index with reduced noise and is adjusted for land climate, ecology, and weather conditions. This index provides a quantitative estimate of weather impact on vegetation and also measures vegetation conditions. Several large-area experiments showed that the VCI had excellent ability to detect drought and to measure the time of its onset and its intensity, duration, and impact on vegetation. The VCI provides accurate drought information not only for the cases with well-defined, prolonged, widespread, and very strong droughts, but also for very localized, short-term, and ill-defined droughts. The advantages of this index compared to conventional ground data are in providing more comprehensive, timely, and accurate drought information. This paper describes the methodology and technical principles used to derive the vegetation condition index, explores data processing, and gives many examples of VCI application for drought monitoring in the United States during 1985–90. The spatial and temporal patterns of VCI-derived drought were in a very good agreement with the identical patterns identified from precipitation and yield anomalies.
Drought is one of the most adverse and powerful weather-related disasters that occur every year across a portion of the United States. The consequences of droughts quite often can be devastating. To mitigate these consequences, droughts require careful monitoring. Recently, NOAA's National Environmental Satellite Data and Information Service developed a new Advanced Very High Resolution Radiometer–based vegetation condition index (VCI) that showed good results when it was used for drought detection and tracking. The VCI is a vegetation index with reduced noise and is adjusted for land climate, ecology, and weather conditions. This index provides a quantitative estimate of weather impact on vegetation and also measures vegetation conditions. Several large-area experiments showed that the VCI had excellent ability to detect drought and to measure the time of its onset and its intensity, duration, and impact on vegetation. The VCI provides accurate drought information not only for the cases with well-defined, prolonged, widespread, and very strong droughts, but also for very localized, short-term, and ill-defined droughts. The advantages of this index compared to conventional ground data are in providing more comprehensive, timely, and accurate drought information. This paper describes the methodology and technical principles used to derive the vegetation condition index, explores data processing, and gives many examples of VCI application for drought monitoring in the United States during 1985–90. The spatial and temporal patterns of VCI-derived drought were in a very good agreement with the identical patterns identified from precipitation and yield anomalies.
The main goal of global agriculture and the grain sector is to feed 6 billion people. Frequent droughts causing grain shortages, economic disturbances, famine, and losses of life limit the ability to fulfill this goal. To mitigate drought consequences requires a sound early warning system. The National Oceanic and Atmospheric Administration (NOAA) has recently developed a new numerical method of drought detection and impact assessment from the NOAA operational environmental satellites. The method was tested during the past eight years, adjusted based on users' responses, validated against conventional data in 20 countries, including all major agricultural producers, and was accepted as a tool for the diagnosis of grain production. Now, drought can be detected 4–6 weeks earlier than before, outlined more accurately, and the impact on grain reduction can be predicted long in advance of harvest, which is most vital for global food security and trade. This paper addresses all these issues and also discusses ENSO impacts on agriculture.
The main goal of global agriculture and the grain sector is to feed 6 billion people. Frequent droughts causing grain shortages, economic disturbances, famine, and losses of life limit the ability to fulfill this goal. To mitigate drought consequences requires a sound early warning system. The National Oceanic and Atmospheric Administration (NOAA) has recently developed a new numerical method of drought detection and impact assessment from the NOAA operational environmental satellites. The method was tested during the past eight years, adjusted based on users' responses, validated against conventional data in 20 countries, including all major agricultural producers, and was accepted as a tool for the diagnosis of grain production. Now, drought can be detected 4–6 weeks earlier than before, outlined more accurately, and the impact on grain reduction can be predicted long in advance of harvest, which is most vital for global food security and trade. This paper addresses all these issues and also discusses ENSO impacts on agriculture.
Drought is the most damaging environmental phenomenon. During 1967–91, droughts affected 50% of the 2.8 billion people who suffered from weather-related disasters. Since droughts cover large areas, it is difficult to monitor them using conventional systems. In recent years the National Oceanic and Atmospheric Administration has designed a new Advanced Very High Resolution Radiometer- (AVHRR) based Vegetation Condition Index (VCI) and Temperature Condition Index (TCI), which have been useful in detecting and monitoring large area, drought-related vegetation stress. The VCI was derived from the Normalized Difference Vegetation Index (NDVI), which is the ratio of the difference between AVHRR-measured near-infrared and visible reflectance to their sum. The TCI was derived from the 10.3–11.3-μm AVHRR-measured radiances, converted to brightness temperature (BT). Algorithms were developed to reduce the noise and to adjust NDVI and BT for land surface nonhomogeneity. The VCI and TCI are used to determine the water- and temperature-related vegetation stress occuring during drought. This paper provides the principles of these indices, describes data processing, and gives examples of VCI–TCI applications in different ecological environments of the world. The results presented here are the first attempt to use both NDVI and thermal channels on a large area with very diversified ecological resources. The application of VCI and TCI are illustrated and validated by in situ measurements. These indices were also used for assessment of drought impact on regional agricultural production in South America, Africa, Asia, North America, and Europe. For this purpose, the average VCI–TCI values for a given region and for each week of the growing season were calculated and compared with yields of agricultural crops. The results showed a very strong correlation between these indices and yield, particularly during the critical periods of crop growth.
Drought is the most damaging environmental phenomenon. During 1967–91, droughts affected 50% of the 2.8 billion people who suffered from weather-related disasters. Since droughts cover large areas, it is difficult to monitor them using conventional systems. In recent years the National Oceanic and Atmospheric Administration has designed a new Advanced Very High Resolution Radiometer- (AVHRR) based Vegetation Condition Index (VCI) and Temperature Condition Index (TCI), which have been useful in detecting and monitoring large area, drought-related vegetation stress. The VCI was derived from the Normalized Difference Vegetation Index (NDVI), which is the ratio of the difference between AVHRR-measured near-infrared and visible reflectance to their sum. The TCI was derived from the 10.3–11.3-μm AVHRR-measured radiances, converted to brightness temperature (BT). Algorithms were developed to reduce the noise and to adjust NDVI and BT for land surface nonhomogeneity. The VCI and TCI are used to determine the water- and temperature-related vegetation stress occuring during drought. This paper provides the principles of these indices, describes data processing, and gives examples of VCI–TCI applications in different ecological environments of the world. The results presented here are the first attempt to use both NDVI and thermal channels on a large area with very diversified ecological resources. The application of VCI and TCI are illustrated and validated by in situ measurements. These indices were also used for assessment of drought impact on regional agricultural production in South America, Africa, Asia, North America, and Europe. For this purpose, the average VCI–TCI values for a given region and for each week of the growing season were calculated and compared with yields of agricultural crops. The results showed a very strong correlation between these indices and yield, particularly during the critical periods of crop growth.
