Monitoring Drought from Space
Drought is the world’s most destructive natural hazard and has had devastating impacts on food security and food production. Episodes of drought increased in frequency and intensity over the past two decades as a result of climate change, and this trend is expected to continue.
Timely and reliable information on the condition of food crops all over the world is essential for mitigating the impact of agricultural drought.
Agriculture Stress Index System (ASIS)
FAO’s Global Information and Early Warning System (GIEWS) and the Climate, Energy and Tenure Division developed a system for detecting agricultural areas with a high likelihood of water stress - drought at global, regional and country level.
By monitoring vegetation indices across global crop areas during the growth season, ASIS can detect “hotspots” around the globe where crops may be affected by drought.
ASIS allows countries to fine-tune parameters of the system based on detailed land use maps and national crop statistics. At the country level, ASIS could be used in developing a remote sensing-based index for crop insurance.
The Agricultural Stress Index System (ASIS) is based on 10-day (dekadal) satellite data of vegetation and land surface temperature from the METOP-AVHRR sensor at 1 km resolution.
The development of ASIS is included in the EU/FAO Programme on “Improved global governance for hunger reduction”
ASIS is based on the Vegetation Health Index (VHI), derived from NDVI and developed by Kogan from the Center for Satellite Applications and Research (STAR) of the National Environmental Satellite, Data and Information Service (NESDIS). This index was successfully applied in many different environmental conditions around the globe, including Asia, Africa, Europe, North America and South America.
VHI can detect drought conditions at any time of the year. For agriculture, however, we are only interested in the period most sensitive for crop growth, so the analysis is performed only between the start (SOS) and end (EOS) of the crop season (temporal integration) and restricted to crop areas (spatial integration). ASIS assess the severity (intensity, duration and spatial extent) of the agricultural drought and express the final results at administrative level giving the possibility to compare it with the agricultural statistics of the country.
Operational outputs of Global ASIS:
The operational products of ASIS are available every 10-day on the GIEWS Earth Observation website.