1) The document discusses drought indicators and indices that can be used in drought early warning systems. It provides examples of commonly used indices for meteorological, agricultural, soil moisture, and hydrological drought monitoring. 2) Indices are categorized by inputs required, ease of use, and applications. No single indicator can determine drought impacts or responses, so using multiple indices is best. 3) Quantitative triggers based on index values are favored for initiating predetermined actions in drought plans. Monitoring is essential for risk management and response cannot be implemented without ongoing measurement and assessment of drought conditions.

1. Overview of Drought Indicators and
their Application in the Context of a
Drought Early Warning and
Information System
Mark Svoboda, Climatologist/Monitoring Program Area Leader
National Drought Mitigation Center
NOAA’s Drought Risk Management Research Center
University of Nebraska-Lincoln
NENA Regional Water/Drought Platform Stakeholders Workshop
Cairo, Egypt, October 27-29, 2015

2. The Cycle of Disaster Management

5. Provide a template for action that
countries can use in the development of a
national drought management policy and
drought preparedness/mitigation plans
The process is structured in 10 steps
that can be adapted by countries to reflect
their institutional, infrastructure, legal,
socio-economic and environmental
context
Case studies from Brazil, Mexico,
Morocco and the USA and will be
continuously updated based on the
experiences gained in the guidelines’
application
The guidelines respond to a need for
action oriented drought policies
IDMP Guidelines

6. Drought Plan Components
Monitoring and early warning
Integrate and distill information
Assess, communicate, and trigger action
Foundation of a drought mitigation plan
Vulnerability assessment
Who and what is at risk and why?
Mitigation and response actions
Actions/programs that reduce risk and
impacts and enhance recovery
Most processes and plans in the past have
primarily focused on monitoring and response...

7. The Importance of Drought
Early Warning and Information
Systems (DEWIS)
Allows for early drought detection
Improves response (proactive)
Data and tools for decision support
“Triggers” actions within a drought plan
A critical mitigation action
Foundation of a drought plan

8. Components of a Drought Early
Warning and Information System
(DEWIS)
Monitoring AND Forecasting
Access to timely data (including impacts)and
“value added” information
Synthesis/analysis of data used to “trigger”
set actions within a drought plan
Tools for decision makers
Efficient dissemination/communication
(WWW, media, extension, etc.)
Drought risk assessment and planning
Education and Awareness

9. Types of Drought:
Meteorological
Agricultural
Hydrological
Socioeconomic
There are indicators and indices for
all of these types of drought
There is no one definition of drought
Thus, there is typically no “one size
fits all” drought index or indicator

10. Spatial Extent

11. Definitions: Indicators, Indices
and Triggers
Indicators: Variables or parameters
used to describe drought conditions.
(NOTE: Indices are Indicators as well)
Examples: precipitation, temperature,
streamflow, groundwater, reservoir levels,
snowpack, soil moisture, drought indices, etc.
Indices: Typically a computed numerical
representation of a drought’s
severity/intensity using climatic,
hydrologic, or remotely sensed inputs.

12. Definitions: Indicators, Indices
and Triggers
Triggers: Specific values of an
indicator/indice that initiate and/or
terminate each level of a drought plan,
and associated management responses.
Who is accountable to do what
and when?
Ties back to the plan!
Examples: 6-mo SPI below the 5th percentile for
two consecutive months Level 4 Drought
OR…
3-mo SPI above the 30th percentile for
three consecutive months No Drought

13. What Questions Do Drought
Indicators/Indices Help Answer?
How does the drought compare historically?
How often does a drought of this magnitude
happen? (frequency/return periods)
When was the last time a drought like this
happened? (analogs)
What did the spatial footprint of the last
drought look like? (areal extent via maps)
Expand drought planning horizons?
Add paleo (tree rings) data in the future?

14. Importance of Drought Indices
Simplify complex relationships
and provide a good communication
tool for diverse audiences/users
Quantitative assessment of
anomalous climatic conditions
Intensity
Duration
Spatial extent
Historical reference (probability
of recurrence)
Planning and design applications

15. Considerations for Choosing
Indicators / Triggers
Proper and Timely Detection of Drought
Spatial and Temporal Sensitivity
Supplies and Demands
Drought In / Drought Out
Composite and/or Multiple Indicators
Data availability/stability, period of record,
and validity
Ease of Implementation
Validation….do they match the
impacts/reality of the situation on the
ground?

16. Approaches to Drought Assessment
Single index or indicator (parameter)
Multiple indices or indicators
Assessed stand-alone
Composite (or “hybrid”) Indicator
Blended approach

17. http://www.droughtmanagement.info/

18. The purpose of this handbook is to identify
some of the most commonly used
physically-based drought
indicators/indices that are being applied
across drought-prone regions with the goal
of advancing monitoring, early warning and
information delivery systems in support of
risk-based drought management policies
and preparedness plans.
Monitoring Drought: A Handbook
of Indicators and Indices

19. The guide is intended to be used by the
general drought practitioner (e.g.
Meteorological/Hydrological service,
Ministry level, resource managers and
other decision makers at various levels)
and was intended to serve as a
potential starting point to determine
which indicators/indices are available
and being put into practice around the
world.
Monitoring Drought: A Handbook
of Indicators and Indices

20. The indicators and indices covered are
aimed at the physical nature of drought
and do not cover overlap issues
such as climate change,
vulnerability assessment, risk,
aridity, desertification or water
scarcity, all of which play a role in how
drought needs to be monitored and
addressed.
Monitoring Drought: A Handbook of
Indicators and Indices

21. The indicator/index types are grouped
into the following classifications:
which directly correspond to the
meteorological, agricultural and
hydrological drought types: 1)
temperature and/or precipitation; 2)
soil moisture; 3) hydrological; 4)
satellite and vegetation; and 5)
composite, modeled or experimental
Monitoring Drought: A Handbook of
Indicators and Indices

22. For the “ease of use” classification, a “traffic
light” approach for each indicator/index was
adopted where:
Green: Indices are considered to be green if
one or more of the following criteria apply:
Code or program to run the index is readily and
freely available
Does not require daily data
Does allow for missing data
Output of the index is already being produced
operationally and is made available on the web
Monitoring Drought: A Handbook of
Indicators and Indices

23. Note: While a “green” ease of use
classification may imply that the
indicator/indice may be the easiest to
obtain or use, it does not mean it is
the best index/indicator for any given
region or locale. This decision as to
which indicator(s)/indices to use has
to be determined by the user and
depends on the given application(s).
Monitoring Drought: A Handbook of
Indicators and Indices

24. Yellow: Indices are considered to be
yellow if one or more of the following
criteria apply:
Multiple variables or inputs needed for calculations
Code or program to run the index is not available
in a public domain
May only need a single input or variable, but no code
is available
The complexity of the calculations needed to
produce the index is minimal
Monitoring Drought: A Handbook of
Indicators and Indices

25. Red: Indices are considered to be red if one
or more of the following criteria apply:
Would need to develop code to calculate the
index based upon the methodology in the
literature
The index or derivative products are not readily
available
An obscure index which is not widely used, but
may be applicable to some
Any index which contains modeled input or is
part of the calculations
Monitoring Drought: A Handbook
of Indicators and Indices

26. Meteorological
Based Page
Ease
of
Use
Inputs
Required Additional Information
Aridity Anomaly
Index (AAI) Green P,T, PET, ET Operationally available for India
Deciles Green P
Ease of calculation and examples from
Australia useful
Keetch-Byram
Drought Index (KBDI) Green P,T
KBDI calculations are based upon the
climate of the area of interest
Percent of Normal
Precipitation Green P Simple calculations
Standardized
Precipitation Index
(SPI) Green P
The WMO highlighted the SPI as a starting
point for meteorological drought
monitoring
Weighted Anomaly
Standardized
Precipitation (WASP) Green P,T
Uses gridded data in monitoring drought in
tropical regions
Aridity Index (AI) Yellow P, T
Can also be used in climate classifications
China Z Index (CZI) Yellow P
Intended to improve upon what the SPI
provides
Crop Moisture index
(CMI) Yellow P,T Weekly values are needed
Drought Area Index
(DAI) Yellow P
Gives an indication of how the monsoon
season perform
Drought
Reconnaissance Index
(DRI) Yellow P, T
Monthly temperature and precipitation
needed
Effective Drought
Index (EDI) Yellow P
Program is available through direct contact
with originator
Hydro-Thermal
Coefficient (HTC) Yellow T,P
Ease in calculations and several examples in
Russia
NOAA Drought Index
(NDI) Yellow P
Best used in agricultural applications
Palmer Drought
Severity Index (PDSI) Yellow P,T, AWC
Not green due to complexity of calculations
and the need for serially complete data
Palmer Z Index Yellow P,T, AWC
One of the many outputs of the Palmer
Drought Severity Index calculations
Rainfall Anomaly
Index (RAI) Yellow P Serially complete data required
Self-Calibrated
Palmer Drought
Severity Index (sc-
PDSI) Yellow P,T, AWC
Not green due to complexity of calculations
and serially complete data needed
Standardized
Anomaly Index (SAI)
Yello
w P
Point data used to describe regional
conditions
Standardized
Precipitation
Evapotranspiration
Index (SPEI)
Yello
w P, T
Serially complete data required, output
similar to the SPI but with a
temperature component
Agricultural
Reference Index for
Drought (ARID) Red P,T, Mod
Regionally produced in the
southeastern United States and not
tested widely outside of the region
Crop Specific
Drought Index
(CSDI) Red
P,T,Td,W,
Rad,AWC,
Mod,crop
data
Quality data of many variables needed,
making its use a challenge
Reclamation
Drought Index (RDI) Red P,T,S,R, SF
Similar to the SWSI, but contains a
temperature component
Soil Moisture Based
Ease
of
Use
Inputs
Needed Additional Information
Soil Moisture
Anomaly (SMA)
Yello
w P,T, AWC
Intended to improve upon the water
balance of the PDSI
Evapotranspiration
Deficit Index (ETDI) Red Mod
Complex calculations with multiple
inputs needed
Soil Moisture
Deficit Index (SMDI) Red Mod
Weekly calculations at different soil
depths, complicated to calculate
Soil Water Storage
(SWS) Red
AWC,RD,S
T,SWD
Due to variation in both soil and crop
types, interpolation over large areas is
challenging
Hydrological Based
Ease
of
Use
Inputs
Needed Additional Information

27. Index Name: Aridity Anomaly Index (AAI)
Ease of use: Green
Origins: Developed in India by the India Meteorological Department (IMD).
Characteristics: A real time drought index in which the water balance is considered. The Aridity Index
(AI) is computed for each week or bi-weekly period. For each period, the actual aridity for the period is
compared to the normal aridity for that period. Negative values indicate a surplus of moisture while
positive values indicate moisture stress.
Input parameters: Actual evapotranspiration and calculated potential evapotranspiration, which would
require temperature, wind, and solar radiation values.
Applications: Agricultural drought, especially in the tropics where defined wet and dry seasons are part
of the climate regime. Both the winter and summer cropping seasons can be assessed with this method.
Strengths: Specific to agriculture, the calculations are simple and the description of drought (mild,
moderate, severe) is based on the departure from normal. Will respond quickly with a weekly time step.
Weaknesses: Not applicable to long-term or multi-seasonal events.
Resources: http://www.imdpune.gov.in/research/drought/drought.html
References:
Indicator Summaries…

28. 1) Typically, No single indicator/index is
used solely in determining appropriate
actions
2) Instead, different thresholds from
different combinations of inputs is the
best way to approach monitoring and
triggers using a variety of indices and
indicators
3) Decision making (or “triggers”) based
on quantitative values are supported
favorably and are better understood
Critical Observations:

29. Lessons Learned
Monitoring is the foundation of risk
management planning
Trigger for who does what and when!
One can not manage what is not
monitored….and you can’t monitor
what you don’t measure!

30. Mark Svoboda
msvoboda2@unl.edu
402-472-8238
http:/drought.unl.edu
Questions?
Photo Credit: Daniel Griffin