The ENSO-TC teleconnection in HiGEM

Ray BellSupervisors: 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- ENSO-large scale environmental parameters- Final work chapter: GCM experiments

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?

Sep 2013

Jan 2013

Previous work: ENSO-TCASO

JFM

NCEP re-an (‘50-’05)GPI. Camargo (2007)

Gray; Klotzbach; Landsea Chan; Liu Gray; Camargo

Singh; Chian

Kuleshov; Vitart

Nicholls; Ramsay

El Nino La Nina

Shaman and Maloney (2011) Shortcomings in climate model simulations of the ENSO-Atlantic hurricane teleconnection. J. ClimCMIP3 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

Idealised GCM simulationHiGEMUK’s High-Resolution Global Environmental Model (Shaffrey et al, 2009)

HiGAM: AMIP (atmospheric model forced with observed SST and sea ice) 1979-2002 (Strachan et al, 2011)

1.25ox0.83o, ∆x50N = 90 km

1/3o ocean model HiGEM 1.1 CTRL 150 yrs

HiGEM CTRL ~5x30 yrs

N144

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

Tracking algorithm (TRACK; Bengstton et al, 2007)

A 20 year time-slice of GCM simulated tropical storms

HiGEM: ENSO simulationShaffrey (2009)

ENSO composites

IBTrACS (1979-2010)ERA-Interim (1979-2010)NINO-3.4 DJF SSTa > 1oC or < -1oCNH TC season prior to event; SH TC season during eventEl Nino years: 82-83, 86-87, 91-92, 94-95, 97-98, 02-03, 09-10La Nina years: 84-85, 88-89, 98-99, 99-00, 07-08, 10-11

HiGEM: 31 El Ninos, 25 La NinasHiGAM AMIP (79-02): 6 El Ninos, 4 La Ninas

(7)

(6)

HiGEM: TC mean state

Lack ofrecurvature

HiGEM: SST mean state

HiGEM: ENSO-SST

HiGEM: ppt mean state

HiGEM: ppt mean state

HiGEM: ENSO-ppt

HiGEM: Walker Circulation mean state

HiGEM: ENSO-WC

HiGEM: VWS mean state

HiGEM: VWS mean state

HiGEM: ENSO-VWS

HiGEM: 200 hPa Stream function and velocity potential mean state

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)

Idealised El Niño experiments

HiGEM: ENSO simulationShaffrey (2009)

HiGEM: ENSO-SST

HiGEM: ENSO-ppt

HiGEM: ENSO-WC