Monitoring Drought:Current Products and

Technologies

Mark SvobodaNational Drought Mitigation Center

International Drought Information CenterUniversity of Nebraska-Lincoln

Components of a Drought Plan

monitoring, early warning and prediction

risk and impact assessment

mitigation and response

Spatial Extent

Drought Monitoring Questions

Where are we now?

How did we get here?

What is the historical perspective for the current situation?

What are the most likely outcomes from the current situation?

The Importance of a Drought Monitoring System

allows for early drought detection

improves response (proactive)

“triggers” actions within a drought plan

a critical mitigation action

Components of a Drought Monitoring System

timely data and timely acquisition

synthesis/analysis of data used to “trigger” set actions within a plan

efficient dissemination network (WWW, media, extension, etc.)

An integrated climate monitoring system needs to:

be comprehensive in scope (coupling climate, soil and water data)

incorporate local and regional scale data

utilize improved indices and triggering tools (latest technology)

improve impact estimation

be flexible to various user’s needs

Potential Monitoring System Products and Reports

Historical analysis (climatology, impacts, magnitude, frequency)Operational assessment (cooperative data, SPI and other indices, automated networks, satellite and soil moisture data)Predictions/Projections (SPI and other indices, soil moisture, streamflow, seasonal forecasts, SST’s)

Key Variables For Monitoring Drought

climate datasoil moisturestream flowground waterreservoir and lake levelssnow packshort, medium, and long range forecastsvegetation health/stress and fire danger

Importance of Drought Indices

Simplify complex relationships and provide a good communication tool for diverse audiences

Quantitative assessment of anomalous climatic conditions

Intensity

Duration

Spatial extent

Historical reference (probability of recurrence)

Planning and design applications

Triggers: thresholds determining specific, timely actions by decision makers

• appropriate• consistent with impacts• adaptable

Triggers need to be:

Indicators & Triggers Definitions

Indicators: Variables to describe drought conditions.

Examples: precipitation, streamflows, groundwater, reservoir levels, soil moisture, Palmer indices, …

Triggers: Specific values of the indicator that initiate and terminate each level of a drought plan, and associated management responses.

Example: precipitation below the 5th percentile for two consecutive months Level 4 Drought.

(From GA State Plan)

Considerations in Choosing Indicators / Triggers

Proper and Timely Detection of Drought Spatial and Temporal SensitivitySupplies and DemandsDrought In / Drought OutComposite and Multiple IndicatorsData Availability, Validity, and ClarityEase of Implementation

(From GA State Plan)

Problems with Typical Indicators Scales

Drought categories not comparable among indicators

(SPI “extreme” is different than PDSI/PHDI “extreme”)

Varying probability differentials for equal index differentials

(SPI –2 to –1 is 13.6%; SPI –1 to 0 is 34.1%)

Lack of temporal and spatial consistency

PDSI, extreme drought: < 1% , Jan., Northwest; > 10%, July, Midwest

SPI Drought Category Cumulative Frequency

0.00 to – 0.99 Mild 16%-50%

–1.00 to –1.49 Moderate 6.8%-15.9%

–1.50 to –1.99 Severe 2.3%-6.7%

–2.00 or less Extreme < 2.3%

PDSI/PHDI Drought Category Cumulative Frequency

0.00 to –1.49 Mild 28%-50%

–1.50 to –2.99 Moderate 11%-27%

–3.00 to –3.99 Severe 5%-10%

–4.00 or less Extreme < 5%

(From GA State Plan)

Problems with Typical Indicators Scales

Difficulty using multiple indicators

(Indicators units not validly combined; Triggers not statistically comparable)

DroughtCategory SPI Streamflow

(cfs)Groundwater

(ft)Reservoir Level

(ft)

Mild (1) 0.00 to – 0.99 > 1000 < 45 > 1065

Moderate (2) –1.00 to –1.49 700 - 1000 45 - 50 1055 - 1065

Severe (3) –1.50 to –1.99 400 - 700 50 - 55 1050 - 1055

Extreme (4) –2.00 or less < 400 > 55 < 1050

(From GA State Plan)

A Solution: Indicators Based on Percentiles

Raw indicator data converted to percentiles (cumulative frequency)

Triggers based on percentile thresholds for each Drought Category (level)

Triggers for each indicator correspond to those percentiles

(e.g., groundwater level of 51.1 ft. is the 35th percentile; 54.0 ft.is the 20th percentile)

DroughtCategory

Percentile SPI Streamflow(cfs)

Groundwater(ft)

ReservoirLevel (ft)

Mild (1) 0.20 – 0.35 - 0.39 1346 51.1 1062.6

Moderate (2) 0.10 – 0.20 - 0.84 518 54.0 1061.1

Severe (3) 0.05 – 0.10 - 1.28 267 56.3 1058.4

Extreme (4) 0.00 – 0.05 - 1.64 160 57.7 1056.5

(From GA State Plan)

Drought Levels(based on percentiles)

Percentile0.50-1.00

0 0.35-0.501 0.20-0.352 0.10-0.203 0.05-0.104 0.00-0.05

Level 2 Level 3 Level 4

Category Normal/Wet

Near-normal/dryLevel 1

(From GA State Plan)

Triggering GoalsAdvance warning going in (while avoiding false alarms)

Conservative going out (while avoiding unnecessary restrictions)

Smooth transition going in and going out

Ease of understanding and implementation

Trigger in: from less severe to more severe drought level

Trigger out: from more severe to less severe drought level

Consistent with historic conditions

Which triggers would have performed “best”?

(From GA State Plan)

Triggering Sequence Methodology

Drought “in’ and “out” triggers:

• For going into a drought ("in" triggers): When any one of the triggers is at a certain (or more severe) level for at least two consecutive months, then that level is invoked. The primary "in" trigger is the SPI-6, unless another trigger invokes Level 1 first. In that case, the other trigger becomes the primary trigger until the SPI-6 catches up (to an equal or more severe level), and then takes over.

• For getting out of a drought ("out" triggers): When all of the triggers are at a certain (or less severe) level for at least four consecutive months, then that level is invoked. The first "out" trigger should be the first "in" trigger. Then additional "out" triggers need to be met before moving to a less severe level of drought.

(From GA State Plan)

Future Needs and Recommendations

Real-time testing of triggersFeedback from stakeholdersCoordination at different scalesData collection and analysesSupplement to human expertise

(From GA State Plan)

Triggers: State of South CarolinaIncipient Drought Alert Phase:PDI -.50 to -1.49CMI 0.00 to –1.49SPI -1.0 to –1.49KBDI 300 to 399Drought Monitor D0ADS is 111-120% of the minimum flow for 2 consecutive weeksSWL in aquifer is between 11 to 20 ft. above trigger level for 2consecutive months

Moderate Drought Alert Phase:PDI -1.50 to –2.99CMI -1.50 to –2.99SPI -1.50 to –2.00KBDI 400 to 499Drought Monitor D1ADS 101-110%/SWL 1-10 ft above trigger level

Triggers: State of South CarolinaSevere Drought Alert Phase:PDI -3.00 to –3.99CMI -3.00 to –3.99SPI -2.01 to –2.99KBDI 500 to 699Drought Monitor D2ADS between min flow and 90% of the min flow for 2 consecutive weeksSWL between trigger level and 10 ft. below trigger levelfor 2 consecutive monthsExtreme Drought Alert Phase:PDI -4.00 and belowCMI -4.00 and belowSPI -3.00 and belowKBDI 700 and aboveDrought Monitor D3/D4ADS < 90% of min flow/SWL > 10 ft. below trigger level

Triggers: Denver Water

80 percent full Mild drought

60 percent full Moderate drought

40 percent full Severe drought

If predicted or actual July 1 storage is below…

Declaration would be...

Considerations for Selecting a Specific Trigger or Index:

Is the information readily available?Can an index/trigger be calculated in a timely manner? Is the information likely to remain available over time?Is the information likely to remain available over time? Can the index/trigger be meaningfully correlated to actual conditions?

1) No single parameter 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

3) Decision making (or “triggerstriggers”) based on quantitative values are supported favorably and are better understood

Critical Observations:

Approaches to Drought Assessment

Single index or parameter

Multiple indices or parameters

Composite index

Mark Svoboda National Drought Mitigation Center

Making the Drought Monitor:Putting the Pieces Together

With ContributionsFrom:

Richard Heim,NCDC

David Miskus,CPC-JAWF

Brad Rippey,USDA-JAWFMike Hayes,

NDMCDoug LeComte,

CPCRich Tinker,

CPC

The Drought Monitor Overview

History – Background - Objectives

Participants

Procedure

Input Indicators

User Feedback

Challenges

The U.S. Drought MonitorSince 1999, NOAA (CPC and NCDC), USDA, and the

NDMC have produced a composite drought map -- the U.S. Drought Monitor -- each week with input from

numerous federal and non-federal agencies

Why the Recent Interest in Drought in the U.S.?

Single and multi-year severe droughtsintensity and duration

western and eastern U.S.

Spatial extent—40 to 50% of U.S. in 2002

Complexity of impacts VulnerabilityAgriculture, energy, transportation, urban water supply, recreation/tourism, fires, environmental, social

Conflicts between water users

Water restrictions (agricultural and urban)

Trend toward drought mitigation planning

Media coverage

Why Monitor Drought?

Drought is a Normal Part of the Climatic CycleDrought Impacts are Significant & WidespreadMany Economic Sectors AffectedDrought is Expensive

Since 1980, major droughts and heat waves within the U.S. alone have resulted in costs exceeding 100 billion dollars

Recent Drought Lossesin the U.S.

1988: $39.2 billion nationwide

1993: $1 billion across the Southeast

1996: $10 billion across the Southwest

1998: $6-8 billion across the South

1999: $1 billion along the East Coast

2000: $1 billion each in Nebraska, Oklahoma, Texas, and Georgia

2002: >$20 billion nationwide??

2003: $$ billion ????Average annual losses: $6-8 billion (FEMA)

Original Objectives

“Fujita-like” scale

U.S. Drought Monitor Map

Drought Intensity Categories

D0 Abnormally Dry

D1 Drought – Moderate

D2 Drought – Severe

D3 Drought – Extreme

D4 Drought – Exceptional

Original Objectives

“Fujita-like” scale

NOT a forecast!

Identify impacts (A, H)

Assessment of current conditions

Incorporate local expert input

Be as objective as possible

Drought Severity Classifications

**Indices used primarily during the snow season and in the West include the River Basin Snow Water Content, River Basin Average Precipitation and SWSI

U.S. Drought Monitor Several key and ancillary indicators Attempts to capture conditions across wide

spectrum of drought conditions

Must Address: No single definition

of drought Integrates many

indicators Now creating in

ARC GIS

Indices for“The West”

Other Drought Indicators (Used with Caution):

Reservoir levelsGround Water levelsStreamflow levelsSatellite SSMI Wetness

Objective BlendsOperationally integrate multiple indicators in

a weekly update using a percentile ranking method

Produced weekly using CPC’s real-time daily and weekly climate division data and NCDC’s monthly archive of indices for 1932-2000

All parameters are first rendered as percentiles with respect to 1932-2000 data using a percent rank method

Short- and Long-Term Blends produced

Objective Blends

Short-Term Blend

35% Palmer Z Index25% 3-Month Precip.20% 1-Month Precip.13% CPC Soil Model7% Palmer Drought Index

Objective Blends

Long-Term Blend

25% Palmer Hydrological Index20% 24-Month Precip.20% 12-Month Precip.15% 6-Month Precip.10% 60-Month Precip.10% CPC Soil Model

ObjectiveBlends

Useful for showing situations and areas having similar trends or opposite trends in moisture conditions

Monitor Development Development (Period starts 12Z last Tuesday)(Period starts 12Z last Tuesday)

Monday (5 Days available)

Draft map sent to local experts

ThursdayFinal map & text released on NDMC Website

Tuesday (6 Days available)

Local expert feedbackDraft map sent to local expertsDraft text sent to local experts

Wednesday (7 Days available; ending 12Z yesterday)

Local expert feedback Draft map(s) sent to local experts Draft text(s) sent to local experts (Outlook) Final map and text sent to secured ftp server

The Importance of Local Expert Input

The National Centers can produce a variety of input indicator products(e.g., CPC station dot map)These give us “The Big Picture”

The Importance of Local Expert Input

The U.S. Drought Monitor Team Relies on Field Observation Feedback from the Local Experts for Impacts Information & “Ground Truth”

Listserver (140-150 Participants: 2/3 Federal, 1/3 State/Univ.)

Local NWS & USDA/NRCS Offices

State Climate Offices

State Drought Task Forces

Regional ClimateCenters

Midwest Regional Climate Center

The Importance of Local Expert Input

High PlainsRegional

Climate Center

The Importance of Local Expert Input

Western Regional Climate Center Colorado Climate Center

The Importance of Local Expert Input

Montana StateDrought Advisory Committee

Oregon State Climatologist Office

Observed real-time data are essential:for timely drought assessments (real-time and historical)for increased spatial and temporal resolutionas input for generating many climate products/forecasts “ground truthing” of soil moisture (and other) models“ground truthing” of radar precipitation estimatesgetting information to decision makers when they need it…….i.e. yesterday!filling in data sparse areas

Real-Time NWS Cooperative Real-Time NWS Cooperative Observer NetworkObserver Network

www.coop.nws.noaa.gov

Automated Weather Networks

Automated Weather Networks

Mesonet Sites Approx. 1,000 in the U.S.

http://drought.unl.edu/dm

Future Challenges

Incorporate groundwater, streamflow, reservoirs, AHPS data as more real-time

data become available

Develop a sister hydro DM equivalent: The Water Resources Monitor??

Support and utilize the development of a western SWSI tool (BWI—Basin Water Index)

Incorporate USDA soil moisture (i.e. SCAN) and/or Mesonet soils data

Next Steps

North American DM is currently being produced “experimentally”

Taking the DM into a new spatial realm?

Robust IMS/GIS query/analysis potential

ACIS---Applied Climatological Information System. Effort taking daily climate data from NOAA’s COOP network, SCAN, SNOTEL, along with state and regional Mesonet data

Incorporate new tools: ACIS, remote sensing, NADSS, soil moisture sensors, etc.

National Drought Mitigation Centerhttp://drought.unl.edu/dm

http://drought.unl.edu