The US CLIVAR Working Group on
Drought
USCLIVAR Annual Summit
Annapolis, MD
15-17 July 2009
Siegfried Schubert (NASA/GMAO) and Dave Gutzler (Univ New Mexico)
Cochairs
U.S. Membership
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Tom Delworth
NOAA GFDL
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Rong Fu
Georgia Institute of Technology
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Dave Gutzler (co-chair) University of New Mexico
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Wayne Higgins
NOAA/CPC
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Marty Hoerling
NOAA/CDC
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Randy Koster
NASA/GSFC
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Arun Kumar
NOAA/CPC
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Dennis Lettenmaier University of Washington
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Kingtse Mo
NOAA CPC
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Sumant Nigam
University of Maryland
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Roger Pulwarty
NOAA- NIDIS Director
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David Rind
NASA - GISS
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Siegfried Schubert (co-chair) NASA GSFC
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Richard Seager
Columbia University/LDEO
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Mingfang Ting
Columbia University/LDEO
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Ning Zeng
University of Maryland
International Membership: Ex Officio
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Bradfield Lyon
International Research Institute for Climate
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Victor O. Magana Mexico
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Tim Palmer
ECMWF
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Ronald Stewart
Canada
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Jozef Syktus
Australia
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Jose Marengo
CPTEC/INPE
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Jean-Philippe Boulanger Univ. of Buenos Aires
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Hugo Berbery
Univ. of Maryland
Other interested participants:
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Jin Huang Jin.Huang@noaa.gov
Adam Sobel <ahs129@columbia.edu>
Max Suarez <Max.J.Suarez@nasa.gov>
***Phil Pegion pegion@gmao.gsfc.nasa.gov
Entin, Jared K. <jared.k.entin@nasa.gov>
Donald Anderson <donald.anderson-1@nasa.gov>
Rong Fu rf66@mail.gatech.edu
Doug Lecomte Douglas.Lecomte@noaa.gov
***Hailan Wang hwang@climate.gsfc.nasa.gov
Junye Chen jchen@gmao.gsfc.nasa.gov
Eric Wood efwood@princeton.edu
Aiguo Dai adai@ucar.edu
Alfredo Ruiz-Barradas <alfredo@atmos.umd.edu>
Jae Kyung E Schemm Jae.Schemm@noaa.gov
Kirsten L. Findell <Kirsten.Findell@noaa.gov>
Accomplishments
• DWG Web page:
– http://www.usclivar.org/Organization/drought-wg.html
– List of relevant model simulations and observational data sets
• Coordinated Model simulations
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GMAO, GFDL, NCAR, CPC, Lamont, COLA/U Miami
Impact of SST and Land/atmosphere feedbacks
http://gmao.gsfc.nasa.gov/research/clivar_drought_wg/index.html
Subset of data available to public
ftp://gmaoftp.gsfc.nasa.gov/pub/data/clivar_drought_wg/
• CDPW 2008 : Focus workshop on drought (with DRICOMP)
– 08 Spring “USCLIVAR Variations”: US CLIVAR Drought Working
Group Workshop
Publications
– U.S. CLIVAR VARIATIONS
• 07 Spring: The U.S. CLIVAR Working Group on Long-term Drought –
D.Gutzler and S. Schubert
• 08 December: Overview of the Drought Working Group
• 08 December: Analysis of the multi-model U.S. CLIVAR Drought
Working Group Simulations – P. Pegion and A. Kumar
– Special Issue in JCLIM (DWG and DRICOMP)
• 10 publications in various stages of review from DWG (see next slide)
• 10 publications in various stages of review from DRICOMP
– Other:
• Koster, R. D., Z. Guo, R. Yang, P. A. Dirmeyer, K. Mitchell, and M. J.
Puma, 2009: On the nature of soil moisture in land surface models. J.
Climate, in press.
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1) Siegfried Schubert, and the extended drought working group: A USCLIVAR Project to Assess and Compare the Responses
of Global Climate Models to Drought-Related SST Forcing Patterns: Overview and Results. Accepted (pdf).
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2) Kingtse C. Mo, Jae-Kyung E. Schemm and Soo-Hyun Yoo: Influence of ENSO and the Atlantic multi-decadal Oscillation
on Drought over the United States. Submitted (pdf).
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3) Randal Koster, Hailan Wang, Siegfried Schubert, Max Suarez and Sarith Mahanama: Drought-Induced warming in the
continental United States under different SST regimes. Accepted.
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4) Hailan Wang, Siegfried Schubert, Max Suarez and Randal Koster: The Physical Mechanisms by which the Leading Patterns
of SST Variability Impact U.S. Precipitation. Submitted (pdf).
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5) Yochanan Kushnir, Richard Seager, Mingfang Ting, Naomi Naik, and Jennifer Nakamura: Mechanisms of Tropical Atlantic
SST Influence on North American Hydroclimate Variability. Submitted (pdf).
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6) Philip Pegion and Arun Kumar: Multi-model Estimates of Atmospheric Response to Modes of SST Variability and
Implications for Droughts. Submitted (pdf).
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7) Scott Weaver, Siegfried Schubert and Hailan Wang: Warm Season Variations in the Low-Level Circulation and
Precipitation over the Central U.S. in Observations, AMIP Simulations, and Idealized SST Experiments. Accepted (pdf).
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8) Kirsten L. Findell and Thomas L. Delworth: Impact of common sea surface temperature anomalies on global drought and
pluvial frequency. Submitted (pdf).
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9) Matias Mendez and Victor Magana: Regional aspects of prolonged meteorological droughts over Mexico. Submitted (pdf).
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10) Alfredo Ruiz-Barradas and Sumant Nigam: AMIP Simulations of 20th Century North American Precipitation Variability
by the Drought Working Group Models. Submitted.
Leading EOFs and Time series (annual mean SST - 1901-2004)
Linear
Trend
Pattern
(LT)
Pacific
Pattern
(Pac)
Atlantic
Pattern
(Atl)
Idealized Experiments
PacInd
NATL
SST Forcing patterns
(warm phase)
NATL
PacInd
warm
neutral cold
warm
ww
wn
neutral
nw
cold
wc
cw
nc
cn
cc
Annual Mean 200mb Height Response (m)
Pacific Warm
Pacific Cold
Global Spatial Correlations of Annual
Mean Responses
Precipitation
Agreement
among models
for response to
Pacific is high
Agreement is
higher for z200
than it is for
precipitation
Agreement among
models for
response to
Atlantic is lower
z 200mb
U.S. Precipitation Response (mm/day)
U.S. Tsfc Response (mm/day)
CCM3
NSIPP1
GFS
GFDL
CAM3.5
The annual and continental United States mean responses for precipitation (top panel) and surface
temperature (bottom panel) for all 8 combinations of the Pacific and Atlantic patterns for the 5 AGCMs
Optimal SST Forcing for Drought in US
°C
Annual Precipitation (mm/day)
Pacific Cold+Atlantic Warm
US Drought!
Pacific Warm+Atlantic Cold
US Pluvials!
Precipitation Response (mm/day) During SON: PcAw
mm/day
850mb Wind Speed (m/s) and Streamlines During SON
m/s
Impact of Soil Moisture Feedbacks - Response to Cold Pacific in JJA
With Soil Moisture Feedback
No Soil Moisture Feedback
Major drought in
Great Plains
Reduced severity
of drought in
Great Plains
mm/day
Optimal SST Forcing for Drought in US
With Feedback
Without Feedback
What Have We Learned?
• Important Role of SST in Droughts and Pluvials World-Wide
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Dominant role of tropical Pacific SST
Important role of the tropical Atlantic/IAS
Important role of land-atmosphere feedbacks
Strong seasonality of responses (seasonally-changing impacts of planetary
waves, jetstream dynamics/large-scale subsidence, weather, low level
circulations/LLJs, land-atmosphere feedbacks, predictability)
– General agreement among models on global response, but substantial
differences on regional scales
• Over the US
– Models agree that:
• Cold Pacific+Warm Atlantic => drought/warm
• Warm Pacific+Cold Atlantic => pluvial conditions/cold
– The models disagree on the regional details:
• Sensitivity to errors in stationary waves
• Sensitivity to strength of land-atmosphere coupling
• Sensitivity to low level response in the IAS/Caribbean
Future Directions
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Much more to study in current idealized and AMIP-style runs
– Physical mechanisms linking SST, Impact of land
– Other parts of the world (focus was on response over North America)
– ftp://gmaoftp.gsfc.nasa.gov/pub/data/clivar_drought_wg/
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Continue Focus on:
– Dependence on Time scales: Seasonal, Inter-annual, Decadal/Climate Change
– AGCM: response to SST, stationary waves, warm season precipitation, roles of different ocean
basins including IAS, land-atmosphere coupling strength
– Coupled model issues: realistic SST variability, +AGCM issues
– Resolution issues: e.g. diurnal cycle, mesoscale, LLJ, role of weather
– Role of land: soil moisture, vegetation, aerosols
– Observations: soil moisture monitoring and ICs: role of LDAS, satellite measurements, improved
information/inferences about coupling strength
– Other quantities (snow, run-off, temperature, etc)
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Programs/related activities
– Drought interest group (CLIVAR/GEWEX)
– VAMOS panel on extremes, IASCLIP
– AR5 IPCC runs including decadal simulations