NOAA's environmental satellites, widely known for their role in weather forecasting, were recently hailed by countries around the world for providing early warning of drought. Satellite-based information from NOAA provides drought warnings four to six weeks earlier than ground-based data, NOAA reported today.

Returning from a recent meeting of the World Meteorological Organization, Felix Kogan, of NOAA's National Environmental Satellite, Data, and Information Service, reported that NOAA's satellite-based system is the only global system available that can provide such early warnings. Kogan was one of 25 world experts from 12 countries who assessed the current status of drought early warning systems at the WMO meeting in Lisbon.

"Many countries around the world depend on data from NOAA's environmental satellites to provide estimates of drought onset, dynamics, intensity, and geographic areas affected," Kogan said. "NOAA provides images outlining vegetation stress and makes estimates of the percent of a country affected by droughts of different severity. In addition, we make comparative analyses of the time the drought started, and the intensity and speed at which it develops."

After a relatively quite year in 1999, the year 2000 has seen a series of extreme droughts. The country of Georgia, a former republic of the U.S.S.R. and now a member of the Commonwealth of Independent States, which produces excellent varieties of grapes for wine-making and produces grains and vegetables, was hit by an unusually intensive drought. "Considering the severity of the disaster and a lack of infrastructure, the government of Georgia asked NOAA to estimate the drought consequences," Kogan said.

In addition to Georgia, Northern America, sub-Sahara Africa, southeastern and central Asia were among the regions of the world most seriously affected. Severe vegetation stress has been persisting since spring around and south of the Caspian Sea, western India, most of Mongolia, and adjacent areas of China. In the Horn of Africa, nearly 15 million people were affected from unusual drought which resulted in crop failures earlier this year in Ethiopia. Nearly 60 percent of Kenya was affected by extreme drought, the largest area since 1991. Afghanistan and Pakistan had severe vegetation stress due to lack of precipitation and excessive heat since mid-February. In the United States, in addition to crop and pasture failures in the southeastern and central states, drought caused large areas of intensive fires in the northwest.

Poland and Morocco both requested NOAA's help in providing digital data on vegetation health in order to estimate possible crop losses. During Kogan's visit to China in May 2000, officials in the province of Jillin (eastern China) requested NOAA's assistance in estimating the areas under drought, the intensity and duration, which were provided several times during the growing season. Digital data were also sent to Kazakhstan; drought estimates were provided to Tajikistan.

"The NOAA/NESDIS drought product became popular worldwide because of its exceptional quality, real-time availability, and ease of use," said Kogan. "The success came after scientists from NOAA cooperated with world researchers and users in testing and calibrating the product comprehensively against ground data."

The product is based on the normalized difference vegetation index (NDVI) developed by NASA in the late 1970s. The NDVI became a popular tool in many countries for analysis of vegetation distribution and conditions. As time progressed, and the technology and the science became more sophisticated, it became evident that NDVI alone was not sufficient for early drought detection and assessment of the impacts because ambient temperature played an important role. Therefore, in the late 1980s NOAA/NESDIS scientists improved drought detection and monitoring techniques adding thermal information from the radiances measured by an instrument known as the AVHRR on NOAA's polar-orbiting satellites.

"Compared to other techniques, the new method permitted us to identify drought up to six weeks earlier, delineate areas more accurately, and provide numerical estimates of the impacts on environment, agriculture, forestry and human health. In the past six years, the new method of early drought detection and watch was used globally to make some important decisions. In Poland, this method has been used since 1997 for assessment of drought impacts on crop condition and estimating crop production. During an intensive 1998 drought in Mexico, this method was used by the government for making important decisions on implementing an alternative crop program.

More information on the NOAA/NESDIS drought product is online at:
http://orbit-net.nesdis.noaa.gov/crad/sat/surf/vci/index.html