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Ray Bell Supervisors: Prof. P.L. Vidale, Dr. Kevin Hodges, Dr. Jane Strachan

The role of the eastern tropical Pacific on typhoon activity associated with different types of El Niño. Ray Bell Supervisors: Prof. P.L. Vidale, Dr. Kevin Hodges, Dr. Jane Strachan. Thanks to Hillary Weller and Eric G uilyardi. PhD.

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Ray Bell Supervisors: Prof. P.L. Vidale, Dr. Kevin Hodges, Dr. Jane Strachan

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  1. The role of the eastern tropical Pacific on typhoon activity associated with different types of El Niño Ray Bell Supervisors: Prof. P.L. Vidale, Dr. Kevin Hodges, Dr. Jane Strachan Thanks to Hillary Weller and Eric Guilyardi

  2. PhD How does the El Niño Southern Oscillation (ENSO) influence global tropical cyclone activity? What is the role of the eastern tropical Pacific on typhoon activity associated with different types of El Niño. What is the response of tropical cyclones to climate change?

  3. Different types of El Niño Ashok et al 2007 1951, 1957, 1965, 1972, 1976, 1982, 1987, 1997 1969, 1991, 1994, 2002, 2004 Wang el 2007

  4. Different types of El Niño • Various definitions: • e.g. Kug et al (2009) EP-EN NINO3 > NINO3std & CP-EN NINO4 > NINO4std • Kao and Yu (2009) combined regression–EOF • Ren and Jin (2011) new Niño indices, piecewise linear combination of the Niño3 and Niño4 indices • Kug and Ham (2011) EP-EN DJF SSTa norm NINO3 > 1 & NINO3>NINO4 • CP-ENDJF SSTa norm NINO4 > 1 & NINO4>NINO3 (& _20W) • Distinctly different types of ENSO, or whether there is one type of ENSO with variability in its location?

  5. Typhoon activity associated with different types of El Niño Kim et al 2011 Pradhan (2011) Jin (2013)

  6. Drivers of Typhoon activity associated with different types of El Niño Kim et al (2011) Wang et al (2013)

  7. Drivers of Typhoon activity associated with different types of El Niño CP-EN • Baroclinic model (dynamic core of the Geophysical Fluid Dynamics Laboratory AGCM, T42) • Heating anomaly experiments • Day 30 are shown as the steady responses. heating profiles imposed at σ = 0.5 and the 850-hPa anomalous winds EP-EN Chen and Tam (2011)

  8. Modelling typhoon activity associated with different types of El Niño Jin et al (2013) Hong et al (2012) • ECHAM5, T42 • 6-member ensemble • Global-exp and WNP-exp, observed global monthly SSTA pattern (CP-EN minus EP-EN) and local SSTA pattern in WNP • WRF RCM with 50-km horizontal CP-EN minus EP-EN Remote SST is important Local SST is important

  9. 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

  10. 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

  11. Different types of El Niñoin HiGEM • EP-ENDJF SSTa norm NINO3 > 1 • & NINO3>NINO4 • CP-ENDJF SSTa norm NINO4 >1 • & NINO4>NINO3 • (& _20W) Kug and Ham (2011)

  12. Ideas for experiments Hill et al (2011) Spencer et al (2003)

  13. El Niño experiments Tukey filter

  14. Tropical cyclone density

  15. Tropical cyclone genesis

  16. Walker circulation Kim (2011)

  17. Upper-level circulation

  18. Precipitation

  19. OLR Pradhan (2011)

  20. Steering flow and GPH Jin (2013)

  21. Relative humidity Kim (2011)

  22. Discussion and conclusion • HiGEM-HiGAM simulates TCs moving towards SE Asia in CP-EN, similar to previous studies • For the CP-EN, TC activity is dominated by SST in the tropical eastern Pacific. • The pattern strengthens in the case of the tCP-EN experiment. • The influence is mainly through strengthening the anomalous cyclonic response in the Philippine sea. • For the EP-EN local SST is (most/just?) as important as the warm SSTs in the tropical eastern Pacific. • SSTs are cooler in the WPAC during EP-EN compared to CP-EN. • The influence is through a change in local thermodynamic parameters (RH); Steering flow is mostly unchanged

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