Agricultural Drought Indices - US Department of Agriculture

the-clock nature of WIGOS, the analytical capability of the Global Data Processing System, and
the ability to disseminate the warnings through the Global Telecommunication System form the
basis for early warnings for drought. Plans are aimed at rehabilitating and improving
meteorological observing, telecommunications, data processing, and management and forecasting
facilities, and in developing capability for manufacturing basic equipment and consumables in the
member countries. These measures will no doubt contribute to the improvement of the quality and
quantity of data and products available to the NMHSs and to user communities as well as regional
and global meteorological centers.
WMO actively involves the NMHSs, the regional and sub-regional meteorological centers, and
other bodies in the improvement of hydrological and meteorological networks for systematic
observations and exchange and analysis of data. WMO also works closely with other UN agencies
and international organizations to develop long-term strategies aimed at promoting meteorological
and hydrological activities that contribute to better drought monitoring and use of medium- and
long-range weather forecasts and to assist in the transfer of knowledge and technology.
Role of NMHSs in Drought Monitoring, Risk Assessment, and Early Warning
WMO’s Agricultural Meteorology Programme and the Hydrology and Water Resources Programme
work through the NMHSs in drought preparedness and drought management. The provision of
meteorological and hydrological support for drought early warning is perhaps the most
fundamental service supplied by NMHSs, and they contribute to all four phases of Early Warning
Systems (WMO 2000):
a) Mitigation or prevention
b) Preparedness
c) Response
d) Recovery
NMHSs play a crucial role in the drought task force at the national level and provide seasonal
forecasts and early warnings. They help build public awareness of droughts and teach people
about drought. NMHSs provide information on
• Timing of droughts
• Drought intensity
• Drought duration
• Spatial extent of a specific drought episode
• An analysis of the risk of the phenomenon and its likely effect on agricultural production.
The following examples from China, South Africa, and Portugal (WMO 2006) illustrate the role of
NMHSs in the provision of drought monitoring, risk assessment, and early warning.
China
The Beijing Climate Center (BCC) of the China Meteorological Administration (CMA) has used the
Standardized Precipitation Index since 1995 to monitor drought occurrence and development in
China on a 10-day basis. The monitoring results are published in the China Drought Monitoring
Bulletin issued by the BCC. A Chinese drought monitoring and early warning system was
developed between 1995 and 1999 and put into operation on a daily basis in 1999. This system
provides accurate information on drought to various related governmental agencies and to the
general public, which helps in the development of measures to mitigate the impacts of drought.
The core of the system is the Comprehensive Index (CI) for drought monitoring developed by the
BCC as a result of its long experience in drought monitoring and impact assessment. CI is a
function of the last 30-day and 90-day SPI and the corresponding potential evapotranspiration.
Based on CI and soil moisture monitoring from an agricultural meteorological station network and
remote-sensing-based monitoring from CMA’s National Satellite Meteorological Center, a number
of drought monitoring products have been produced:
28