Inter-regional workshop on indices and early warning systems for drought

Background

According to the World Meteorological Organization (WMO), there is an urgent need to develop better drought monitoring and early warning systems. Drought is an insidious natural hazard that results from a deficiency of precipitation from expected or “normal” that, when extended over a season or longer period of time, is insufficient to meet the demands of human activities and the environment. Drought must be considered a relative, rather than absolute, condition. A critical component of national drought strategies should be a comprehensive drought monitoring system that can provide early warning of drought’s onset and end, determine its severity, and deliver that information to a broad group of users in a timely manner. With this information, the impacts of drought can be reduced or avoided in many cases.

One factor that distinguishes drought from other natural hazards is the absence of a precise and universally accepted definition. There are hundreds of definitions, adding to the confusion about whether or not a drought exists and its degree of severity. Definitions also need to be application specific because drought impacts will vary between sectors. Drought means different things to different users such as a water manager, an agricultural producer, a hydroelectric power plant operator, and a wildlife biologist. Droughts are commonly classified by type as meteorological, agricultural, and hydrological and droughts differ from one another in three essential characteristics: intensity, duration, and spatial coverage.

There are numerous natural indicators of drought that should be monitored routinely to determine the onset, ending and spatial characteristics of drought. Severity must also be evaluated on frequent time steps. Although all types of droughts originate from a deficiency of precipitation, it is insufficient to rely solely on this climate element to assess severity and resultant impacts because of factors identified previously. Effective drought early warning systems must integrate precipitation and other climatic parameters with water information such as stream flow, snow pack, ground water levels, reservoir and lake levels, and soil moisture into a comprehensive assessment of current and future drought and water supply conditions.

In February 2009, the WMO Commission for Agricultural Meteorology held an International Workshop on Drought and Extreme Temperatures in Beijing, China to review the increasing frequency and severity of droughts and extreme temperature events around the world. The workshop adopted several recommendations to cope with increasing droughts and extreme temperatures on agriculture, rangelands and forestry. One of the main recommendations was for WMO to make appropriate arrangements to identify the methods and marshal resources for the development of standards for agricultural drought indices in a timely manner.

Specific Workshop Objectives

* To review and assess drought indices currently used around the world for the three types of drought (meteorological, agricultural, and hydrological);

* To review and assess the strengths, weaknesses and limitations of existing drought indices and early warning systems;

* To develop a consensus standard index for each of the three types of drought;

* To develop guidelines for Members in implementing and improving drought early warning systems.

Expected Workshop Outcomes

Several drought experts from each of the six Regions of WMO will be invited to prepare state-of-the-art discussion papers to address the above objectives. Discussions during the workshop will help develop standards for drought indices and guidelines for drought early warning systems. Proceedings of the Meeting will be published by WMO and NDMC and will be widely distributed . Outcomes of the workshop will be presented at a thematic session on drought indices at the Second International Conference on Climate, Sustainability, and Development, in Semi-arid Regions to be held in Fortaleza, Brazil, 16-20, August 2010.