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Africa's Extremely Prolonged Drought

The Horn of Africa – the peninsula loosely comprised of Somalia, Ethiopia, Eritrea, and Djibouti – has been experiencing seemingly unrelenting droughts for decades. Parts of Somalia are plagued with widespread famine due to crop failures, and the U.N. is now involved in airlifting food and aid to the region. Data from NOAA’s satellites has been used by organizations such as the U.N. and USAID to monitor global drought conditions. Satellites can detect drought conditions by measuring either soil moisture or the impacts on vegetation “greenness.” The droughts are then classified in terms of their intensity: abnormally dry, moderate, severe, extreme and exceptional. However, these terms do not consider the length of the drought impact on an area. For example, Texas is currently also experiencing an exceptional, albeit seasonal, drought. With the launch of NOAA-7, the precursor to today’s NOAA-19 and the future JPSS satellites, there have been continuous global measurements of vegetation and drought since 1981. In that time, the Horn of Africa has been under drought conditions classified as extreme for up to 800 weeks (about 15 years), and many other weeks were classified as abnormally dry, severe, or even exceptional. In comparison, small parts of Texas have had extreme droughts for about 300 weeks in that same time period. There is not much improvement expected in the Horn of Africa – another reason for great concern.

Shown here is a plot of the number of weeks that the Horn has experienced extreme drought conditions since data archives began in November of 1981. Extreme droughts are identified as areas with a vegetation health index value from 6-15. Vegetation health indices are derived from the normalized difference vegetation index (NDVI) - the most commonly used satellite dataset for assessing global vegetation condition.

Africa's Extremely Prolonged Drought
 
 
Referral:Global Vegetation Mapping Data from NOAA Satellites
Copyright:National Oceanic and Atmospheric Administration (NOAA) (NOAA Logo)
Keywords:drought, Somalia, NDVI, AVHRR, POES, 2011.07.27

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