1. Hurricanes Working Group Report Suzana J. Camargo Lamont-Doherty Earth Observatory Columbia University Palisades, NY With contributions from all members of the Hurricanes WG U.S. CLIVAR 2011 Summit 18-21 July 2011 Woods Hole, MA

2. US CLIVAR Hurricanes Working Group Formed in January 2011 Co-leaders:  Suzana Camargo, LDEO, Columbia University  Gabriel Vecchi, NOAA GFDL  Kevin Walsh, Melbourne University, Australia

3. Members of CLIVAR working group: James Elsner, Florida State University Kerry Emanuel, MIT James Kossin, NOAA NCDC Christopher Landsea, NOAA AOML Siegfried Schubert, NASA GSFC Adam Sobel, Columbia University Gabriele Villarini, Princeton University Hui Wang, NOAA NCEP Ming Zhao, NOAA GFDL

4. Additional Contributing Members Lennart Bengtsson, U. Reading, UK In-Sik Kang, Seoul National University, Korea K. Oouchi, JAMSTEC, Japan Enrico Scoccimarro, INGV-CMCC, Italy Julio Bacmeister, NCAR Ping Chang and R. Saravanan, Texas A&M Malcolm Roberts, UK Met Office, and Pier Luigi Vidale, U. Reading, UK Christiane Jablonowski U. Michigan and Michael Wehner, Lawrence Berkeley National Lab. Monika Esch, MPI, Germany

5. Terms of reference: Define common experiments for model simulations by participating model groups Supply common data sets and tropical cyclone metrics for those experiments Coordinate the evaluation and reporting of common experiments and the storage of model output Organize a series of workshops to present and discuss the results

6. Hurricane WG - Background: Preliminary attempts of multi-model intercomparison: – TCMIP (K. Walsh) – Discussions: Camargo, Walsh, Schubert, Sobel, Emanuel,... High-resolution global climate models: improved performance simulating tropical cyclone variability (GFDL, FSU, NCEP, Met Office) in interannual and decadal time-scales Vecchi proposed US CLIVAR led the idea of US CLIVAR WG. Significant improvement in an agreeement among models of changes in tropical cyclone activity under climate change:  Intensity: higher occurrence of most intense TCs (globally)  Frequency: smaller global number of TCs (in many models)

7. Dynamical Models Exhibit Skill in Seasonal Basin-wide Hurricane Frequency Statistical-dynamical hybrid model 18-km regional model 100km SST-forced AGCM 50km SST-forced AGCM Figure adapted from Knutson et al (2010, Nat. Geosci.)

8. Problems: CC projections: regional estimates - models diverge Reasons for differences among models' projections are unclear:  Different forcing for future scenarios  Different sensitivity to forcing  Different definitions for TCs TC data – data quality problems, especially out of the Atlantic.

9. Principal Issues Lack of climate-relevant theory of genesis/basin-wide frequency Uncertainty in past (and future) large-scale changes (e.g., SST, upper tropospheric/tropopause layer temperature) Sensitivity studies with AGCMs not coordinated Historical cyclone database corrections adjustments need assessment, continued effort and extension needed (more, different paleo-proxies) Climate predictions/projections beyond frequency (landfall, extremes) Statistical models/downscaling techniques need to be compared and evaluated for skill/relevance to various applications (e.g., prediction, projection, proxy) Coupled model biases in tropical Atlantic Contribution: G. Vecchi

10. Scientific Objectives I An improved understanding of interannual variability, and trends, in tropical cyclone activity from the beggining of the 20 th century to the present. TC response to common increase in SST Sensitivity to differences in SST What is the potential predictability of TCs? Statistics of TCs constrained by SST x stochasticity of the model response

11. Model Response Exhibits Sensitivity To Forcing Used T ropical Storm Frequency Response to Same AGCM but different estimates of observed SST Contribution: G. Vecchi & M. Zhao AGCM is 100km version of Zhao et al (2009, J. Clim.) Obs AGCM Obs AGCM HadISST forcedNOAA-OI.v2 forced

12. Scientific Objectives II Quantifying changes in the characteristics of tropical cyclones under a warming climate. Uniform warming x specific anomalies CO2 x SST warming Relationship between local versus remote forcing in hurricane formation in the Atlantic - tropical mean increase in SST and increase in Atlantic SST only. Remote x local response to SST in other regions of the world.

13. Vecchi, Swanson and Soden (2008, Science) Observed Activity Absolute SST Model Abs. SST High-resolution model activity change Relative SST Model Rel. SST Emanuel et al (08),Knutson et al (08) Oouchi et al (06),Bengtsson et al (07) Contribution: G. Vecchi

14. Idealized Forcing Experiments If local SST the dominant control, as opposed to relative SST: Similar Atlantic Response to Atlantic and Uniform Forcing Little Pacific Response to Atlantic compared to Uniform Contribution: G. Vecchi

15. North Atlantic Response to Idealized SST Atlantic Forcing Uniform Forcing Near-equatorial Forcing Similar TS frequency response to: 0.25° local warming 4° global cooling Contribution: G. Vecchi

16. Participating Models ModelResolution Institution CAM5.20.25 degNCAR, USA CAM5.10.25 degU. Michigan & LBNL, USA CSIRO60kmU. Melbourne, Atlantic ECHAM5T159 L31CMCC INGV, Italy ECHAM6T127 L95MPI, Germany FSU/COAPST126 L27FSU, USA GEOS51/2 degree L72NASA, USA HADGEM360km, L85U. Reading Met Office, UK HIRAM2.150 km L32GFDL, USA NASA GISS1 degree L40NASA GISS, USA NCEP GFST126 L64NCEP, USA NICAM14km L40JAMSTEC, Japan SNU/KAU-AGCM35km, L20SNU, South Korea WRF, domain: Atlantic27kmTexas A&M U., USA

17. Std CAM5 #1 Std CAM5 #2 Std CAM5 #3 IBTraCS Storms with U>33 ms-1: June 1 to Dec 1 2005 Contribution J. Bacmeister

18. Time spent at Categories by tropical cyclones (hours) All basins Northern hemisphere TC season June – Dec Cat1Cat2Cat3Cat4Cat5TSTD 3 CAM5 runs 2005 CAM4 2004, 2005 IBTrACS 2004, 2005 CAM5 no deep conv 2005 CAM5 w/ param condensate loading Hours Defect in tracking algorithm Contribution J. Bacmeister

19. Tropical Cyclones as simulated by CMCC-INGV fully coupled climate models: INGV-SXG (atm: echam4, T106) and CMCC_MED (atm: echam5, T159) -Changes in Tropical Cyclone Activity due to Global Warming: Results from a High-Resolution CGCM. Gualdi et al. 2008 - J. of Climate, Vol. 21, pp. 5204-5228 -Effects of Tropical Cyclones on Ocean Heat Transport in a High Resolution CGCM. Scoccimarro et al. 2011 - J. of Climate, in press. Doi: 10.1175/2011JCLI4104.1 OBS INGV-SXG (T106) CMCC_MED (T159) TCs/y93.866.280.2 STD10.99.27.5 Annual TCs number and variability Hurricane detection in CMCC_MED: 10m wind speed > 33 m/s 1000 Km CMCC_MED TCs annual number and Power Dissipation Index (PDI) 6hourly 10 meter wind speed [m/s] Yearly accumulated PDI [m 3 /s 2 ] TCs Annual Number series Contribution E. Scoccimarro

21. 2005 Atlantic storm track at N512: 5 members initialised on 1 May Contribution: M. Roberts & P.L. Vidale

22. TAMU-CRCM Domain Simulated TC tracks (9km) Simulated TCs are too weak (no Cat-4 & 5 storms) Number of TCs tends to be too high Simulated tracks tend to shift to the north Contribution: P. Chang & R. Saravanan

23. Uncoupled WRF simulations without SST cooling effect over-estimate TC’s intensity and size. Coupled Uncoupled Difference Coupled Uncoupled Contribution: P. Chang & R. Saravanan

24. NICAM 3.5 km mesh 2008/06/20 12UTC TC Fengshen 5 days after the Initial condition

25. TC Fengshen simulation 11-20 June Onset of Western Pacific Monsoon & Weak MJO  equatorial westerly & Weak MJO  equatorial westerly 14 km, 3.5 km Horizontal grid spacing: 14 km, 3.5 km Vertical domain: 0 m ~ 38,000 m (40-levels) Integration: 10 days from 00UTC 15 Jun 2008 Initial conditions: ECMWF YOTC Operational data NCEP final analysis (land surface, SST) Boundary conditions: slab ocean slab ocean (nudging to Reynolds weekly SST) 17 Jun 2008 --- Fengshen formed on 17 Jun 2008 PALAU2008 Field Experiment Contribution: K. Oouchi

26. Tier 1 experiments: 1. Interannual – 20 years (1981-1990) forced with observed SST. 2.Climatology – Climatological SST 3.Global 2K : Climo SST+ Global 2K 4.Double CO2: Climo SST + Double CO2 5.Global 2K & Double CO2: Climo SST+ Global 2K + Double CO2 6. Global Warming: Climo SST + Specified SST anomalies

27. Tier 2 experiments: Atlantic 1K: Climo SST + 1K Atlantic Pacific 1K: Climo SST + 1K Pacific Slab Ocean High Resoluton snapshots Varying horizontal resolutions

28. Diagnostics: Common tracking techniques: 2 – 3 for comparison Dependency of thresholds Large-scale diagnostics: Enviromental variables: vertical shear, humidity, vorticity, precipitation. Genesis Indices Potential intensity ENSO, AMM, AMO, MJO: modulation of TCs in models Statistical-dynamical techniques (Emanuel) Statistical analysis/modeling

29. Where are we now? Bi-monthly teleconferences Webpage in progress Modelling groups running tier 1 experiments (a few are finished). Final negotiation stages for NCDC to archive and host data. ASAP: Model data available for the WG. Next telecon: discussion of diagnostics. 1 st workshop: January 2012 (after annual AMS meeting) Unforseen issue: some groups not sticking to protocol.