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The ENSO-TC teleconnection in HiGEM

The ENSO-TC teleconnection in HiGEM. Ray Bell Supervisors: Prof. P.L. Vidale, Dr. Kevin Hodges and Dr. Jane Strachan. Outline. My PhD Introduction Methodology HiGEM and TRACK Tropical cyclone biases ENSO-Tropical cyclone Mean state biases

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The ENSO-TC teleconnection in HiGEM

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  1. The ENSO-TC teleconnection in HiGEM Ray Bell Supervisors: Prof. P.L. Vidale, Dr. Kevin Hodges and Dr. Jane Strachan

  2. Outline • My PhD • Introduction • Methodology • HiGEM and TRACK • Tropical cyclone biases • ENSO-Tropical cyclone • Mean state biases • ENSO-large scale environmental parameters • Final work chapter: GCM experiments

  3. My PhD • Research questions: • How does ENSO influence global TC activity? • What is the response of TCs to climate change? • What are the implications of a changing El Niño on future tropical cyclone activity? Jan 2013 Sep 2013

  4. Previous work: ENSO-TC El Nino ASO La Nina JFM NCEP re-an (‘50-’05) GPI. Camargo (2007) Gray; Klotzbach; Landsea Chan; Liu Gray; Camargo Singh; Chian Nicholls; Ramsay Kuleshov; Vitart

  5. Shaman and Maloney (2011) Shortcomings in climate model simulations of the ENSO-Atlantic hurricane teleconnection. J. Clim • CMIP3 models. Large-scale fields. No tracks. ‘VWS and PI are most poorly simulated’ • - Simulation of ENSO • Simulation of TC mean state • - Simulation of ENSO teleconnections

  6. Idealised GCM simulation HiGEM UK’s High-Resolution Global Environmental Model (Shaffreyet al, 2009) • HiGAM: AMIP (atmospheric model forced with observed SST and sea ice) 1979-2002 (Strachan et al, 2011) N144 1.25ox0.83o, ∆x50N = 90 km HiGEM CTRL ~5x30 yrs HiGEM 1.1 CTRL 150 yrs 1/3o ocean model

  7. Tracking algorithm (TRACK; Bengsttonet al, 2007) A 20 year time-slice of GCM simulated tropical storms 1) Locate and track all centres of high relative vorticity 35000/yr 2) Apply a 2-day filter to the tracks  8000 storms / yr 3) Analyse vertical structure of storm for evidence of warm-core (tropical storm structure)  120 storms / yr

  8. HiGEM: ENSO simulation • Shaffrey (2009)

  9. ENSO composites IBTrACS (1979-2010) ERA-Interim (1979-2010) NINO-3.4 DJF SSTa > 1oC or < -1oC NH TC season prior to event; SH TC season during event El Nino years: 82-83, 86-87, 91-92, 94-95, 97-98, 02-03, 09-10 La Nina years: 84-85, 88-89, 98-99, 99-00, 07-08, 10-11 HiGEM: 31 El Ninos, 25 La Ninas HiGAM AMIP (79-02):6 El Ninos,4 La Ninas (7) (6)

  10. HiGEM: TC mean state Lack of recurvature

  11. HiGEM: SST mean state

  12. HiGEM: ENSO-SST

  13. HiGEM: ppt mean state

  14. HiGEM: ppt mean state

  15. HiGEM: ENSO-ppt

  16. HiGEM: Walker Circulation mean state

  17. HiGEM: ENSO-WC

  18. HiGEM: VWS mean state

  19. HiGEM: VWS mean state

  20. HiGEM: ENSO-VWS

  21. HiGEM: 200 hPa Stream function and velocity potential mean state

  22. Conclusions • ENSO-SST biases in HiGEM are likely the largest limitation. • Dawson et al (2012) found an increase in oceanic resolution • over atmospheric resolution improved ENSO-extratropical • teleconnections • Atmospheric resolution is also important to capture the interannual variability (therefore response to ENSO; Strachan et al, 2012)

  23. Idealised El Niño experiments

  24. HiGEM: ENSO simulation • Shaffrey (2009)

  25. HiGEM: ENSO-SST

  26. HiGEM: ENSO-ppt

  27. HiGEM: ENSO-WC

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