Global Drought Watch from Space

Abstract

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 10.3-1 \3-jum 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.

Effects of precipitation, temperature and topographic parameters on evergreen vegetation greenery in the Western Ghats, India

“…Myneni et al (1997) found NDVI anomalies over regions of arid and semi-arid land to be correlated with tropical Pacific sea surface temperature. Kogan (1997) confirmed the usefulness of the NDVI-based Vegetation Condition Index (VCI) to assess plant, water and temperature related vegetation stress on several continents. Moulin et al (1997) visualized the phenological evolution (dormancy, growth and vegetation) of global vegetation by analysing the seasonal variation of the NDVI.…”

World droughts in the new millennium from AVHRR‐based vegetation health indices

“…The new AVHRR data-based method of drought warning and surveillance is based on the estimation of green canopy stress from AVHRR-derived indices, characterizing vegetation health, moisture, and thermal conditions [Kogan, 1997[Kogan, ,2001.Unlike the NDVI-based (two spectral channel) approach routinely applied for vege tation monitoring, the new numerical method uses both NDVI and the 10.3-11.3-um infrared channel.The latter provides brightness temperature (BT), which indicates how hot the vegetation canopy can be. In dry years, high temperatures at the background of insuf-VOLUME 83 NUMBER 48…”

“…The details of the algorithm are presented in Kogan [1997Kogan [ ,2001.We mention in this article only the important steps of the process; these include: complete removal of high-frequency noise from NDVI and BT annual time series, approximation of seasonal cycle, and enhancement of medium-to-low frequency fluctuations associated with weather variation. The latter are used as proxies for estimation of vegetation condition and health.Three indices were developed: Vegetation Condition Index (VCI), for estimation of cumulative moisture impacts on vegetation; Temperature Condition Index (TCI), for estimation of thermal impacts; and Vegetation Health Index (VH), for estimation of combined conditions.…”

Drought Hazard Assessment in Ponnaiyar River Basin, India Using Remote Sensing and Geographic Information System

“…The arid tract of western part of India is under threat of severe droughts due to paucity, abnormality of rainfall and severe climatic characteristics (Jain et As the remote sensing technology makes more and more process, with the development of geographic information system (GIS) and Global Positioning System (GPS), the real-time monitoring of drought over the large areas can be achieved. Remote sensing and GIS techniques are increasingly being regarded as a useful drought detection techniques, as evidenced by (Kogan, (1997); Zhang (2004). The main objective of the study was to assess the climate change on drought hazards through normalized weights on three GIS modules i.e.…”