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The indicators and indices listed below are based from the IDMP Handbook on Drought Indicators and Indices and have been drawn from IDMP and partner literature and online searches. They are categorized by type and ease of use, and grouped into the following classifications: (a) meteorology, (b) soil moisture, (c) hydrology, (d) remote sensing and (e) composite or modelled. Although listed by ‘ease of use’, it is possible that any, all or none of the indicators may be suitable for a particular application, based on user knowledge, needs, data availability and computer resources available to implement them. The resource needs increase from green to yellow to red, as outlined below. Again, the simplest index/indicator is not necessarily the best one to use.

IndexesTypeEase of useInput parametersAdditional information
Aridity Anomaly Index (AAI)MeteorologyA Greenprecipitation, temperature, potential evapotranspiration, evapotranspiration Operationally available for India
DecilesMeteorologyA GreenprecipitationEasy to calculation; examples from Australia are useful
Keetch-Byram Drought Index (KBDI)MeteorologyA Greenprecipitation, temperatureCalculations are based upon the climate of the area of interest
Percent of Normal PrecipitationMeteorologyA GreenprecipitationSimple calculations
Standardized Precipitation Index (SPI)MeteorologyA GreenprecipitationHighlighted by the WMO as a starting point for meteorological drought monitoring
Weighted Anomaly Standardized Precipitation (WASP)MeteorologyA Greenprecipitation, temperatureUses gridded data for monitoring drought in tropical regions
Aridity Index (AI)MeteorologyB Yellowprecipitation, temperatureCan also be used in climate classifications
China Z Index(CZI)MeteorologyB YellowprecipitationIntended to improve upon SPI data
Crop Moisture Index(CMI)MeteorologyB Yellowprecipitation, temperatureWeekly values are required
Drought Area Index(DAI)MeteorologyB YellowprecipitationGives an indication of monsoon season performance
Drought Reconnatissance Index(DRI)MeteorologyB Yellowprecipitation, temperatureMonthly temperature and precipitation are required
Effective Drought Index (EDI)MeteorologyB YellowprecipitationProgram available through direct contact with originator
Hydro-thermal Coefficient of Selyaninov (HTC)MeteorologyB Yellowprecipitation, temperatureEasy calculations and several examples in the Russian Federation
NOAA Drought Index (NDI)MeteorologyB YellowprecipitationBest used in agricultural applications
Palmer Drought Severity Index (PDSI)MeteorologyB Yellowprecipitation, temperature, available water contentNot green due to complexity of calculations and the need for serially complete data
Palmer Z IndexMeteorologyB Yellowprecipitation, temperature, available water contentOne of the many outputs of PDSI calculations
Rainfall Anomaly Index (RAI)MeteorologyB YellowprecipitationSerially complete data required
Self-Calibrated Palmer Drought Severity Index (sc-PDSI)MeteorologyB Yellowprecipitation, temperature, available water contentNot green due to complexity of calculations and serially complete data required
Standardized Anomaly Index (SAI)MeteorologyB YellowprecipitationPoint data used to describe regional conditions
Standardized Precipitation Evapotranspiration Index (SPEI)MeteorologyB Yellowprecipitation, temperatureSerially complete data required; output similar to SPI but with a temperature component
Agricultural Reference Index for Drought (ARID)MeteorologyC Redprecipitation, temperature, modelledProduced in south-eastern United States of America and not tested widely outside the region
Crop-specific Drought Index (CSDI)MeteorologyC Redprecipitation, temperature, dew point temperature, solar radiation, available water content, modelled, crop dataQuality data of many variables needed, making it challenging to use
Reclamation Drought Index (RDI)MeteorologyC Redprecipitation, temperature, snowpack, reservoir, streamflowSimilar to the Surface Water Supply Index, but contains a temperature component
Soil Moisture Anomaly (SMA)Soil moistureB Yellowprecipitation, temperature, available water contentIntended to improve upon the water balance of PDSI
Evapotranspiration Deficit Index (ETDI)Soil moistureC RedmodelledComplex calculations with multiple inputs required
Soil Moisture Deficit Index (SMDI)Soil moistureC RedmodelledWeekly calculations at different soil depths; complicated to calculate
Soil Water Storage (SWS)Soil moistureC Redavailable water content, reservoir, soil type, soil water deficitOwing to variations in both soil and crop types, interpolation over large areas is challenging
Palmer Hydrological Drought Severity Index (PHDI)HydrologyB Yellowprecipitation, temperature, available water contectSerially complete data required
Standardized Reservoir Supply Index (SRSI)HydrologyB YellowreservoirSimilar calculations to SPI using reservoir data
Standardized Streamflow Index (SSFI)HydrologyB YellowstreamflowUses the SPI program along with streamflow data
Standardized Water-level Index (SWI)HydrologyB YellowgroundwaterSimilar calculations to SPI, but using groundwater or well-level data instead of precipitation
Streamflow Drought Index (SDI)HydrologyB YellowstreamflowSimilar calculations to SPI, but using streamflow data instead of precipitation
Surface Water Supply Index (SWSI)HydrologyB Yellowprecipitation, reservoir, streamflow, snowpackMany methodologies and derivative products are available, but comparisons between basins are subject to the method chosen
Aggregate Dryness Index (ADI)HydrologyC Redprecipitation, evapotranspiration, streamflow, reservoir, available water content, snowpackNo code, but mathematics explained in the literature
Standardized Snowmelt and Rain Index (SMRI)HydrologyC Redprecipitation, temperature, streamflow, modelledCan be used with or without snowpack information
Enhanced Vegetation Index (EVI)Remote sensingA GreensatelliteDoes not separate drought stress from other stress
Evaporative Stress Index (ESI)Remote sensingA Greensatellite, potential evapotranspirationDoes not have a long history as an operational product
Normalized Difference Vegetation Index (NDVI)Remote sensingA GreensatelliteCalculated for most locations
Temperature Condition Index (TCI)Remote sensingA GreensatelliteUsually found along with NDVI calculations
Vegetation Condition Index (VCI)Remote sensingA GreensatelliteUsually found along with NDVI calculations
Vegetation Drought Response Index (VegDRI)Remote sensingA Greensatellite, precipitation, temperature, available water content, land cover, evapotranspirationTakes into account many variables to separate drought stress from other vegetation stress
Vegetation Health Index (VHI)Remote sensingA GreensatelliteOne of the first attempts to monitor drought using remotely sensed data
Water Requirement Satisfaction Index (WRSI and Geo-spatial WRSI)Remote sensingA Greensatellite, modelled, crop coefficientsOperational for many locations
Normalized Difference Water Index (NDWI) and Land Surface Water Index (LSWI)Remote sensingA GreensatelliteProduced operationally using Moderate Resolution Imaging Spectroradiometer data
Soil Adjusted Vegetation Index (SAVI)Remote sensingC RedsatelliteNot produced operationally
Combined Drought Indicator (CDI)Composite or modelledA Greenmodelled, precipitation, satelliteUses both surface and remotely sensed data
Global Integrated Drought Monitoring and Prediction System (GIDMaPS) Composite or modelledA Greenmultiple, modelledAn operational product with global output for three drought indices: Standardized Soil Moisture Index, SPI and Multivariate Standardized Drought Index
Global Land Data Assimilation System (GLDAS)Composite or modelledA Greenmultiple, modelled, satelliteUseful in data-poor regions due to global extent
Multivariate Standardized Drought Index (MSDI)Composite or modelledA Greenmultiple, modelledAvailable but interpretation is needed
United States Drought Monitor (USDM)Composite or modelledA GreenmultipleAvailable but interpretation is needed