The US CLIVAR Drought Working Group usclivar/Organization/drought-wg.html
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Transcript of The US CLIVAR Drought Working Group usclivar/Organization/drought-wg.html
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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.html
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• Bradfield Lyon International Research Institute for Climate • Victor O. Magana Mexico • Tim Palmer ECMWF • Ronald Stewart Canada • Jozef Syktus Australia
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Other interested participants• Lisa Goddard <[email protected]> • Alex Hall <[email protected]> • Jerry Meehl <[email protected]>• Jin Huang <[email protected]>• John Marshall <[email protected]> • Adam Sobel <[email protected]>• Max Suarez <[email protected]>• Phil Pegion <[email protected]>• Tim Palmer <[email protected]>• Entin, Jared K. <[email protected]>• Donald Anderson <[email protected]> • Rong Fu <[email protected]>• Doug Lecomte <[email protected]>• Hailan Wang <[email protected]>• Junye Chen <[email protected]>• Eric Wood <[email protected]>• Aiguo Dai <[email protected]>• Alfredo Ruiz-Barradas <[email protected]>• Jae Kyung E Schemm <[email protected]>• Clara Deser [email protected]• Kirsten Findell <[email protected]>• Mark Helfand [email protected]• Scott J. Weaver <[email protected]>• Kit K. Szeto <[email protected]>• Chunzai Wang <[email protected]>• Adam Phillips <[email protected]>• Matias Mendez <[email protected]>• Hugo Berbery <[email protected]>
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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_drought_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
Warm Atlantic
Neutral Atlantic
Cold Atlantic
Warm Pacific
PwAw PwAn PwAc
Neutral Pacific
PnAw PnAn
Control
PnAc
Cold Pacific
PcAw PcAn PcAc
- 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
z 200mb
Agreement among models for response to Pacific is high
Agreement among models for response to Atlantic is lower
Agreement is higher for z200 than it is for precipitation
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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 Cold+Atlantic Warm Pacific Warm+Atlantic Cold
US Drought! US Pluvials!
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Some Basic Results: Over US
• Mean Responses– Models tend to agree that
• Cold Pacific+Warm Atlantic => drought/warm• Warm Pacific+Cold Atlantic => 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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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.
Annual Mean Precipitation and 200mb Eddy Height Climatologies
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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)
Tsfc
Precip
warm Pacific
cold Pacific
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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 Cold+Atlantic Warm Pacific Warm+Atlantic Cold
US Drought! US Pluvials!
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Seasonal Evolution of Response
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DJF - Cold
Weak and shifted anti-cyclonic anomalies
Contours: 200mb height anomalies
Vectors: 850mb wind anomalies
Colors: precipitation 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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DJF MAM
JJA SON
Great Plains(Seasonality of Response)
warm Pacificcold Pacific
Tsfc
Precip
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Predictability Measures
Signal to Noise Ratio
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R = ( x-y )/sxy
( ): 50 yr mean
x: seasonal mean from experiment
y: seasonal mean from control (climatological SST)
s2xy = (s2
X+s2Y)/2
s2X variance of seasonal mean from experiment
s2Y : variance of seasonal mean from control
Signal to Noise Ratio ( R)
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GP SESW
NW
Focus U.S. Response to Pacific Forcing
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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