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Tropical Cyclones and Climate Change in a High Resolution General Circulation Model, HiGEM

Tropical Cyclones and Climate Change in a High Resolution General Circulation Model, HiGEM. Ray Bell Supervisors: Prof. Pier Luigi Vidale, Dr. Kevin Hodges and Dr. Jane Strachan MO TCWG 1/3/12. Introduction. Research Objectives

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Tropical Cyclones and Climate Change in a High Resolution General Circulation Model, HiGEM

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  1. Tropical Cyclones and Climate Change in a High Resolution General Circulation Model, HiGEM Ray Bell Supervisors: Prof. Pier Luigi Vidale, Dr. Kevin Hodges and Dr. Jane Strachan MO TCWG 1/3/12

  2. Introduction • Research Objectives • Investigate the changes in TC activity (location, frequency, intensity and structure) with climate change. • Investigate a change of natural variability mechanisms on TC activity e.g. ENSO. And the types of El Niño. • Work Completed Since Last Meeting • Investigating the chain of mechanisms which gives rise to the change in TC activity. • Understanding natural variability (ENSO) in HiGEM. • Adding HiGEM1.2 to the current study

  3. Idealised GCM simulations HiGEM UK’s new High-Resolution Global Environmental Model (Shaffreyet al, 2009) HiGEM 4xCO230 yrs HiGEM Transient 2% CO2/yr 70 yrs HiGEM 2xCO230 yrs 1.25ox0.83o, ∆x50N = 90 km HiGEM CTRL ~9x30 yrs 1/3o ocean model HiGEM 1.1 CTRL 150 yrs HiGEM 1.2 CTRL 117 yrs

  4. Understanding natural variability • ENSO’s impact on geographical location

  5. Understanding natural variability • ENSO’s impact on TC frequency

  6. Climate Change Simulations • Change in geographical location Stippling if outside 9x30yr CTRL variability

  7. Climate Change Simulations • Change in TC frequency Error bars are max and min of 9x30 yr CTRL variability

  8. Sea Surface Temperature Difference Jul-Oct 2xCO2 - CTRL 4xCO2 - CTRL Sea Surface Temperature Difference (°C) • Tongue of relatively less warm water compared to the rest of the tropics • Grave results of TCs in this vicinity (NAtl). • Leads to increased vertical wind shear (VWS) via thermal wind balance

  9. Vertical Wind Shear Difference Jul-Oct 2xCO2 - CTRL 4xCO2 - CTRL Vertical Wind Shear difference (m/s) Stippling if outside 5x30yr CTRL variability • VWS spreads to the NEPac especially in the 4xCO2 • Detrimental affect on TCs. • Reduced VWS in CPac favours development

  10. Walker CirculationDifference Jul-Oct 0-10N° 2xCO2 - CTRL 4xCO2 - CTRL -ω difference (Pa/s) and divU difference (m/s) • Weakening of the tropical circulation inline with other studies (Vecchi and Soden, 2007) • Favours development in the CPac and reduces TC frequency is the NWPac

  11. Investigating Other Parameters NAtl NEPac

  12. Conclusion • A tongue of relatively less warm water in the tropical NAtl increases VWS and decreases upward motion which reduces the frequency. • The increase in VWS spreads to the NEPac in the 4xCO2 • A weaker Walker circulation suppresses activity in the NWPac and enhances activity in the NCPac. • Future work • Continue Adding HiGEM1.2 onto my current study. • Investigate the different types of El Niño and the impact they have on TC activity. How these change with climate change.

  13. Comparison to obs IBTrACS (’79-’02) ERA-Interim (’79-’10) HiGEM CTRL 150 years Track density

  14. Climate Change Simulations

  15. Klotzbach and Gray (2011) AMO ~= AMOC

  16. Change in SST Zhao et al (2009)

  17. Change in vws Vecchi et al (2007)

  18. Change in RH700 Vecchi et al (2007)

  19. Change in –ω500

  20. Change in ppt

  21. 2 types of ENSO in HiGEM Kug and Ham (2011) • Investigate change in TC activity with the 2 types of El Nino. • Investigate the change in types of ENSO in HiGEM inc. CO2 and the TC relation

  22. Large scale tropical change

  23. Change in duration

  24. Regional Change in duration

  25. Change in structure 100 most intense TCs at most intense Earth relative winds Below 35oN NH Avg 30 yr ctrl 4xCO2 2xCO2 10o radius 850hPa

  26. TRACK Hodges (1995); Bengstssonet al. (2007) • T42 ξ850 – Reduce noise. Comparison of different spatial resolution data • Minimum lifetime of 2 days and no constraint on the minimum displacement distance. Capture more of TC lifecycle • Cyclogenesis (0-30oN over ocean) • Coherent vertical structure and warm core • Max T63 vor at each level from 850hPa to 250hPa • Intensity threshold T63 ξ850 > 6x10-5 s-1, ξ850 – ξ200 > 6x10-5 s-1 , for at least 1 day (4 x 6hr). • Search for warm core between p levels 850-500, 500-200hPa (+ ξ value) • Wind speed must attain 20m/s at 850hPa (change in slightly more intense TCs) [att20 dataset] • Statistical packages

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