The USCLIVAR Working Group on Drought: A MultiModel Assessment of the Impact of SST Anomalies on Reg

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The USCLIVAR Working Group on Drought A
Multi-Model Assessment of the Impact of SST
Anomalies on Regional Drought
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The US CLIVAR Drought Working Group
http//www.usclivar.org/Organization/drought-wg.ht
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• U.S. Membership
• Tom Delworth NOAA GFDL
• Rong Fu Georgia Institute of Technology
• Dave Gutzler (co-chair) University of New Mexico
• Wayne Higgins NOAA/CPC
• Marty Hoerling NOAA/CDC
• Randy Koster NASA/GSFC
• Arun Kumar NOAA/CPC
• Dennis Lettenmaier University of Washington
• Kingtse Mo NOAA CPC
• Sumant Nigam University of Maryland
• Roger Pulwarty NOAA- NIDIS Director
• David Rind NASA - GISS
• Siegfried Schubert (co-chair) NASA GSFC
• Richard Seager Columbia University/LDEO
• Mingfang Ting Columbia University/LDEO
• Ning Zeng University of Maryland
• International Membership Ex Officio

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• Other interested participants
• Lisa Goddard ltgoddard_at_iri.columbia.edugt
• Alex Hall ltalexhall_at_atmos.ucla.edugt
• Jerry Meehl ltmeehl_at_ucar.edugt
• Jin Huang ltJin.Huang_at_noaa.govgt
• John Marshall ltjmarsh_at_MIT.EDUgt
• Adam Sobel ltahs129_at_columbia.edugt
• Max Suarez ltMax.J.Suarez_at_nasa.govgt
• Phil Pegion ltpegion_at_gmao.gsfc.nasa.govgt
• Tim Palmer ltTim.Palmer_at_ecmwf.intgt
• Entin, Jared K. ltjared.k.entin_at_nasa.govgt
• Donald Anderson ltdonald.anderson-1_at_nasa.govgt
• Rong Fu ltrf66_at_mail.gatech.edugt
• Doug Lecomte ltDouglas.Lecomte_at_noaa.govgt
• Hailan Wang lthwang_at_climate.gsfc.nasa.govgt
• Junye Chen ltjchen_at_gmao.gsfc.nasa.govgt
• Eric Wood ltefwood_at_princeton.edugt
• Aiguo Dai ltadai_at_ucar.edugt
• Alfredo Ruiz-Barradas ltalfredo_at_atmos.umd.edugt

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Terms of Reference

• propose a working definition of drought and
  related model predictands of drought
• coordinate evaluations of existing relevant model
  simulations
• suggest new model experiments designed to address
  some of the outstanding uncertainties concerning
  the roles of the ocean and land in long term
  drought
• coordinate and encourage the analysis of
  observational data sets to reveal antecedent
  linkages of multi-year drought
• organize a community workshop in 2008 to present
  and discuss results

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Model Experiments

• Force global models with idealized SST anomalies
• Address physical mechanisms, model dependence
• Participating groups/models NASA (NSIPP1),
  Lamont(CCM3), NCEP(GFS), GFDL (AM2.1), NCAR
  (CAM3.5), and COLA/Univ. of Miami/ (CCSM3.0)
• Web site with access to monthly data
  ftp//gmaoftp.gsfc.nasa.gov/pub/data/clivar_drough
  t_wg/README/www/index.html

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Focus Here on Two Leading Patterns of Annual SST
Variability
Pacific Pattern
Atlantic Pattern
?C
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Main Experiments
- REOF patterns superimposed on mean seasonal
cycle with /- 2 std amplitude - e.g., PwAc is
the combined pattern of warm Pacific and cold
Atlantic - all runs 50 years (35 for GFS)
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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
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Warm Pacific
Annual Mean Precip (mm/day) and z200 (5 meter CI)
Response
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Warm Atlantic
Annual Mean Precip (mm/day) and z200 (5 meter CI)
Response
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Annual Precipitation (mm/day)
Pacific ColdAtlantic Warm
Pacific WarmAtlantic Cold
US Drought!
US Pluvials!
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Some Basic Results Over US

• Mean Responses
• Models tend to agree that
• Cold PacificWarm Atlantic gt drought/warm
• Warm PacificCold Atlantic gt pluvial
  conditions/cold
• There are substantial differences in details of
  anomaly patterns
• There is a large seasonality in responses

• Potential Predictability (Pacific signal to
  noise)
• Largest in spring
• Models appear to agree more on precipitation than
  surface temperature responses!

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Special issue highlighting results is now being
put together for J. Climate
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End
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Annual Mean Precipitation and 200mb Eddy Height
Climatologies
The model results are from AMIP-style runs from
each model (runs forced by observed SSTs for the
period 1980-1998). Contour interval for the
height field is 20m (negative values are dashed
and the zero line is the first solid contour).
Precipitation is in mm/day.
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Annual Mean Tsfc Response (C)
Pacific Warm
Pacific Cold
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Annual Mean Tsfc Response (C)
Atlantic Warm
Atlantic Cold
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Great Plains (Annual Mean Response)
warm Pacific
cold Pacific
Precip
Tsfc
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Cold Pacific
Annual Mean Precip (mm/day) and z200 (5 meter CI)
Response
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Cold Atlantic
Annual Mean Precip (mm/day) and z200 (5 meter CI)
Response
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Annual Precipitation (mm/day)
Pacific Cold
Atlantic Warm
Tendency for US Drought!
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Annual Precipitation (mm/day)
Pacific Warm
Atlantic Cold
Tendency for US Pluvials!
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Annual Precipitation (mm/day)
Pacific ColdAtlantic Warm
Pacific WarmAtlantic Cold
US Drought!
US Pluvials!
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Seasonal Evolution of Response
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DJF - Cold
Contours 200mb height anomalies
Vectors 850mb wind anomalies
Colors precipitation anomalies
Weak and shifted anti-cyclonic anomalies
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MAM - Cold
General consistency in height anomalies but CFS
again shifted south
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JJA - Cold
Cyclonic anomalies in IAS
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SON - Cold
Cyclonic anomalies in IAS
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Great Plains (Seasonality of Response)
warm Pacific
cold Pacific
DJF
MAM
Precip
Tsfc
JJA
SON
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Predictability Measures

• Signal to Noise Ratio

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Signal to Noise Ratio ( R)

• R ( x-y )/sxy
• ( ) 50 yr mean
• x seasonal mean from experiment
• y seasonal mean from control (climatological
  SST)
• s2xy (s2Xs2Y)/2
• s2X variance of seasonal mean from experiment
• s2Y variance of seasonal mean from control

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Focus U.S. Response to Pacific Forcing
NW
??
SW
SE
GP
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Precipitation Response to Warm and Cold Pacific
(signal/noise)
R
R
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Tsfc Response to Warm/Cold Pacific (signal/noise)
R
R