The US CLIVAR Working Group on Drought

1. 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

2. 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 • Jose Marengo CPTEC/INPE • Jean-Philippe Boulanger Univ. of Buenos Aires • Hugo Berbery Univ. of Maryland

3. Other interested participants: • 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>

4. Accomplishments • DWG Web page: • http://www.usclivar.org/Organization/drought-wg.html • List of relevant model simulations and observational data sets • Coordinated Model simulations • 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

5. 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.

6. 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). • 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). • 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. • 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). • 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). • 6) Philip Pegion and Arun Kumar: Multi-model Estimates of Atmospheric Response to Modes of SST Variability and Implications for Droughts. Submitted (pdf). • 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). • 8) Kirsten L. Findell and Thomas L. Delworth: Impact of common sea surface temperature anomalies on global drought and pluvial frequency. Submitted (pdf). • 9) Matias Mendez and Victor Magana: Regional aspects of prolonged meteorological droughts over Mexico. Submitted (pdf). • 10) Alfredo Ruiz-Barradas and Sumant Nigam: AMIP Simulations of 20th Century North American Precipitation Variability by the Drought Working Group Models. Submitted.

7. Leading EOFs and Time series (annual mean SST - 1901-2004) Linear Trend Pattern (LT) Pacific Pattern (Pac) Atlantic Pattern (Atl)

8. Idealized Experiments PacInd NATL NATL PacInd SST Forcing patterns (warm phase)

9. Annual Mean 200mb Height Response (m) Pacific Warm Pacific Cold

11. 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

12. 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

13. Optimal SST Forcing for Drought in US °C

14. Annual Precipitation (mm/day) Pacific Cold+Atlantic Warm Pacific Warm+Atlantic Cold US Drought! US Pluvials!

15. Precipitation Response (mm/day) During SON: PcAw mm/day

16. 850mb Wind Speed (m/s) and Streamlines During SON m/s

17. 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

18. What Have We Learned? • Important Role of SST in Droughts and Pluvials World-Wide • 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

19. Future Directions • 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/ • 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) • Programs/related activities • Drought interest group (CLIVAR/GEWEX) • VAMOS panel on extremes, IASCLIP • AR5 IPCC runs including decadal simulations