Agricultural Drought Indices - US Department of Agriculture

October 2008 were almost half the previous three-year minimum and less than a quarter of the
long-term average. In 2010, the worst drought in six decades in southwest China has plunged
more than 2 million people back into poverty. A severe drought has swept the southwestern region,
including Yunnan, Sichuan, and Guizhou provinces; Guangxi Zhuang autonomous region; and
Chongqing municipality.
Because drought affects so many economic and social sectors, scores of definitions have been
developed by a variety of disciplines. Wilhite and Glantz (1985) analyzed more than 150 such
definitions of drought and then broadly grouped those definitions under four categories:
meteorological, agricultural, hydrological, and socio-economic drought.
Losses from extended droughts in the agricultural sector can often amount to hundreds of millions
of dollars. Direct losses result from reduced crop yields, diminished pasture growth, and mortality
of livestock while indirect losses include lost opportunities in agriculture and livestock sectors and
losses to abandonment of land and changes in land use following droughts. According to the U.S.
Federal Emergency Management Agency (FEMA), the United States loses $6-8 billion annually on
average because of drought (FEMA 1995). During the 1998 drought, the state of Texas alone lost
a staggering $5.8 billion (Chenault and Parsons 1998), which is about 39% of the $15 billion
annual agriculture revenue of the state (Sharp 1996). The aggregate impact of drought can be
quite negative on the economies of developing countries, in particular. For example, GDP fell by 8-
9% in Zimbabwe and Zambia in 1992 and 4-6% in Nigeria and Niger in 1984.
This paper presents a short description of the perspectives of the World Meteorological
Organization (WMO) on drought in general and agricultural drought in particular. This is followed
by a short narrative on WMO’s activities in the area of drought.
WMO’s Focus on Drought
As the United Nations specialized agency with responsibility for meteorology and operational
hydrology, WMO, since its inception, has been addressing the issue of droughts. In this respect,
WMO promotes systematic observation, collection, analysis, and exchange of meteorological,
climatological, and hydrological data and information; drought planning preparedness and
management; research into the causes and effects of climate variations and long-term climate
predictions with a view to providing early warning; capacity building; and the transfer of knowledge
and technology.
The fight against drought receives a high priority in the Long-term Plan of WMO, particularly under
the Agricultural Meteorology Programme, Hydrology and Water Resources Programme, and
Technical Cooperation Programme. Within the context of this Plan, WMO continues to encourage
the greater involvement of the national Meteorological and Hydrological Services (NMHSs) and
regional and subregional meteorological and hydrological centers in addressing the issues of
drought.
The Commission for Agricultural Meteorology (CAgM) of WMO has been very active in addressing
the issue of agricultural drought and made recommendations regarding the role of
agrometeorology in helping to solve drought problems in drought-stricken areas, particularly in
Africa. The Commission appointed a number of working groups and rapporteurs with specific
terms of reference. Based on the activities of these working groups and rapporteurs, a number of
reports were published and distributed by WMO.
Working Groups on Drought Appointed by CAgM (1967-2010)
Following are the working groups on drought appointed by CAgM at its sessions since 1967:
a) Fourth Session of CAgM (CAgM-IV) (Manila, Philippines, 1967) – Working Group on
Assessment of Drought
b) CAgM-V (Geneva, Switzerland, 1971) – Working Group on the Meteorological Factors
Concerning Certain Aspects of Soil Deterioration and Erosion
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