Post on 13-Jan-2016
description
Effectiveness of Existing Drought Effectiveness of Existing Drought IndicatorsIndicators
Southeast-ACF Drought Early Warning Information Southeast-ACF Drought Early Warning Information System Development Workshop: Apalachicola River & System Development Workshop: Apalachicola River &
BayBay
April 27-28 2010April 27-28 2010
Apalachicola, FloridaApalachicola, Florida
Douglas Le ComteDouglas Le Comte
NOAA/NCEP Climate Prediction CenterNOAA/NCEP Climate Prediction Center
Douglas.lecomte@noaa.govDouglas.lecomte@noaa.gov
OutlineOutline
• A look at selected current drought indicatorsA look at selected current drought indicators
• An honest appraisal (probably politically incorrect) of An honest appraisal (probably politically incorrect) of how well they work… Doug’s Top 5!how well they work… Doug’s Top 5!
Atlanta Journal Cartoon
Lake Lanier drought index—the keep-it-simple approach
An effective drought index is one that does what you want it to do. You may want to merge several drought indicators to meet your needs, e.g., CPC delivery of historical river basin indices to the water commissions of GA, FL, AL in January 2001.
Desired Features of a Drought Index
• Understandable (what it means and how it’s calculated
• Available daily (short term index) or weekly (long-term index)
• Correlates with impacts
• Range of values easy to understand (e.g., percentiles, anomalies).
• Appropriate spatial resolution
• Can be imported into GIS (e.g. GeoTIFF)
• Has a long history and the archive is easy to find
Historical Perspective* The Drought Phenomenon
Definition – Sectors Impacted – Indices
Early 20th Century Drought Indices Incorporated some measure of precipitation over a given time Examples:
• 15 Consecutive Days with No Rain
• 21 Days or More with Precipitation less than One-Third (or 30%) of Normal
• Annual Precipitation less than 75% of Normal
• Monthly Precipitation less than 60% of Normal
• Any Amount of Rainfall less than 85% of Normal Other important climatic elements (soil
moisture, evapotranspiration, etc.) were not readily available at that time
* R. Heim (Inter-Regional Workshop on Indices andEarly Warning Systems for Drought WMO/NDMC/NOAA/UNCCD/USDALincoln, NE, USA – December 8-11, 2009)
These Basic Indicators Are Still Widely Used Today
Historical PerspectivePalmer’s Drought Index (1965)
and Crop Moisture Index (1968) CMI is computed on a weekly basis
for agricultural applications
Moisture Stress Index Developed in 2003 by NCDC Annual index for corn and soybeans
that relates moisture stress (drought and extreme wetness) to crop productivity Computed from Palmer Z Index and crop yield
Economic impacts
Post-Palmer Era
Indices Based On: Additional Observed Variables
Advanced Statistical Methodologies
More Sophisticated Models
Data from New Observational Platforms
Standardized Precipitation Index (SPI) Developed by Colorado’s McKee et al.
(1993)
Based on Probability Distribution of Precipitation, with Normalization
Can Compute for Different Time Scales for Differing Applications
http://www.ncdc.noaa.gov/oa/climate/research/prelim/drought/spi.htmlhttp://www.wrcc.dri.edu/spi/spi.html
http://www.agr.gc.ca/pfra/drought/mapscc_e.htm
Soil Moisture Soil Moisture Observation Networks Limited in U.S.
http://www.wcc.nrcs.usda.gov/scan/ http://www.cpc.ncep.noaa.gov/products/monitoring_and_data/topsoil.shtml
Soil Moisture Rely on Modeled Soil Moisture
http://www.cpc.noaa.gov/soilmst/leaky_glb.htmhttp://www.cpc.ncep.noaa.gov/products/Soilmst_Monitoring/US/Soilmst/Soilmst.shtmlhttp://mrcc.sws.uiuc.edu/cliwatch/drought/moisture.htmhttp://www.agr.gc.ca/pfra/drought/nlslmr_e.htm
Leaky Bucket Model
CPC “Leaky Bucket”
Using the NLDAS Ensemble Mean Soil Moisture as a Drought Indicator
NCEP Noah
NASA Mosaic
OHD SAC
Princeton VIC
Percentile soil moisture levels correspond to U.S. Drought Monitor levels D0 to D4
Shallow layers of soil moisture can be used as agricultural drought indicators. Model runoff as hydro indicators.
http://www.emc.ncep.noaa.gov/mmb/nldas/drought/
Ensemble Mean
Hybrid Product Integrates Radar Precipitation Estimates with In Situ Rain Gage Measurements
NOAA/NWS Advanced Hydrologic Prediction Service
http://water.weather.gov/index.php
Developed as support for U.S. Drought Monitor Operationally 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
The parameters (drought indicators) are then combined using a weighting scheme
Short- and Long-Term Blends produced
U.S. Objective Blends
http://www.cpc.ncep.noaa.gov/products/predictions/tools/edb/droughtblend-access-page.html
Drought Assessments based on Aggregating Indicators
DWR NC
Based on Streamflow or Groundwater
Groundwater Observing Network Coarse
Hydrologic Indices
http://watermonitor.gov/
Based on Streamflow or Groundwater Streamflow – Need to Remove Peak
Flow from Hydrograph• Streamflow-based drought indicators
usually based on low-flow (base flow) or some averaged flow
Hydrologic Indices
http://watermonitor.gov/
Monthly Average Streamflow14-Day Average Streamflow
FloodMonitoring
DroughtMonitoring
Based on Streamflow or Groundwater Reservoir Data
• State data, no national access system
• Managed for different purposes (irrigation, urban water supply, flood control, etc.)
Hydrologic Indices
http://watermonitor.gov/
Arizona reservoir levels, September 2009, percent of capacity.
Provide Global Coverage Spatially Consistent Reflected Intensities at
Specific Wavelengths
Remotely-Sensed (Satellite-based) Indices
http://www.star.nesdis.noaa.gov/smcd/emb/vci/VH/index.php
http://www.agr.gc.ca/pfra/drought/mapscc_e.htm
Hybrid Drought Index that Integrates: Satellite-based observations of vegetation conditions Climate-based drought index data Biophysical characteristics of the environment
Vegetation Drought Response Index (VegDRI)
http://drought.unl.edu/vegdri/VegDRI_Main.htm
(Source: Wardlow, 2008)
My Top 5 Countdown
No. 5: KBDI
Timely: Daily
Good short term dryness indicator
April 23, 2010: Please Note: Due to technical difficultiesthe KBDI and Rainfall maps are inaccurate.We apologize for any inconvenience.
http://flame.fl-dof.com/fire_weather/KBDI/4km_main.html
No. 4: CPC Drought Indicator Blends
http://www.cpc.ncep.noaa.gov/products/predictions/tools/edb/droughtblend-access-page.html
Weekly, based on Climate Division data; weights somewhat subjective; not operational
No. 3: Soil Moisture Model (CPC)
http://www.cpc.ncep.noaa.gov/products/Soilmst_Monitoring/US/Soilmst/Soilmst.shtml
Daily, with 1-day lag, based on CD data; 1.6m depth; good mid-range indicator. Archive available. But, sometimes not realistic (e.g., see extreme drought in upstate NY).
No.2: NLDAS Soil Moisture
http://www.emc.ncep.noaa.gov/mmb/nldas/drought/
Promising! And yet… min 5-day lag, sometimes much longer; non-operational; very resource intensive, so computer crashes result in huge delays.
No. 1: USGS Streamflowhttp://waterwatch.usgs.gov/
So much to like! Current, real time, daily to 28-days, reliable, percentile format, zoomable,
A Variety of Format Options
Can show in Google Earth as well as Google Maps
Questions?Douglas.lecomte@noaa.govDouglas.lecomte@noaa.gov