UJCC-HiGEM: what is in the treasure chest ?

1. UJCC-HiGEM: what is in the treasure chest ? P.L. Vidale*, M. Roberts+, L. Shaffrey*, W. Norton and J. Slingo * A. Clayton, M.-E. Demory, J. Donners, I. Stevens, D. Stevens *NCAS-Climate, Walker Institute, University of Reading, UK +UKMO Hadley Centre

2. Atmosphere-only integrations: the role of resolution • Matrix of AMIP2-SST forced integrations with increasing resolution: • 25 yrs current climate, completed, climatologies at BADC: • Tropical cyclones (PLV) • Precipitation intensity and frequency, runoff (M-E Demory) • + Land surface processes (PLV+MED) • Mid-latitude storm tracks (Jen Catto, L. Shaffrey) • Blocking (MJR, J. Catto) • Dust and radiation (@1.2, M.W.) • 25 yrs Delta-SST (+4K, -2K), completed, climatologies at BADC • Tropical cyclones (PLV) • In course: 25-yrs HiGEM-SST -> forcing N216 and N96 • Planned in late 2008: Reynolds SSTs (0.25 deg., daily) -> forcing N216 and N96 • Main results: • TCs more intense at higher resolution • Upper quantiles of precipitation appear at high resolution • Quality of runoff improves with resolution • Better Atlantic storm tracks at high-res. • Blocking at high-resolution ? • Changes in TC impacts in warmer world ? ∆x = 135 km ∆x = 90 km ∆x = 60 km Flux coupler Completed in 2007 1o - 1/3o ocean model 1/3o ocean model

3. Had-Hi-NUGAM, MIROC, ECHAM: 100 most intense Tropical Cyclones in 25 yrs Hurricane Mitch 200hPa 200hPa 200hPa 500hPa 500hPa 500hPa 850hPa 850hPa 850hPa 135km resolution 60km HadGAM-HiGAM-NUGAM tangential wind

4. Alpine precipitation in MAM

5. Matrix of coupled models, with increasing resolution (1.1 and 1.2 formulation): • Data: • Science • TIWs in tropical Pacific: MJR (long-term impacts on climate), J.H. (nature of phenomenon) • El Niño: MJR (process and teleconnections in ocean); E-T response to ENSO (UEA) • SST bias improvement and its temporal evolution (D. Stevens) • TCs (only recently started) • MJO (in course) • Mid-latitude storms (J.C. + L.S) • Coastal upwelling (J.D.) • Ocean-atmosphere coupling (D.S. + A.W. + MJR) • Agulhas (S.S.) Coupled simulations in current climate ∆x = 135 km ∆x = 90 km ∆x = 60 km Flux coupler Completed in 2007 1o - 1/3o ocean model 1/3o ocean model

6. Main results from coupled work • El Niño works in HiGEM ! (MJR draft paper) • Frequency characteristics, termination mechanism • Wind stress curl - ocean mixing (DS + A. Dawson, MJR) • Origination mechanism ? • TIWs (MJR, JH papers) • move heat meridionally • Ocean-Atmosphere interaction (JH, LS’s main paper) • Pacific SSTs improved overall (why ?) • Atmospheric variability: improved storm tracks in the Atlantic • Wind stress curl and coastal upwelling (JD, DS) • Improvements in Agulhas retroflection (SS, HC)

7. Sea surface height variability

8. Tropical instability waves • Resolved in HiGEM, poorly resolved in HadGEM; • Responsible for meridional heat transport in the tropical Pacific • Invoked for explaining improved mean state in that region of the ocean, important for El Niño • See papers by M. Roberts and J. Harle

9. Niño3 monthly anomaly spectra: dependence on resolution The low-resolution GCM shows max. power at the wrong frequency. Why ?

10. Coupled HiGEM simulations with +2% CO2/year • Data: • HiGEM1.1 transient currently reached 4xCO2 (~70yrs) • Stabilised and run for 30 years at 2 and 4x CO2 (starting now) • Science: • Ocean heat uptake • What do tropical cyclones look like at 2-4x CO2 *** ? • ENSO • Sea-ice • Precipitation extremes *** • What happens in the upwelling regions ? Suppressed upwelling -> nutrient limitations -> biological deserts ? *** Require ensemble High and dry. 
The least biologically productive regions of the ocean -the subtropical gyres (darkest blue)- are getting bigger. Jeffrey Polovina of the U.S. National Marine Fisheries Service in Honolulu, GRL, 2008 Climate change ∆x = 135 km ∆x = 90 km ∆x = 60 km Flux coupler Completed in 2007 1o - 1/3o ocean model 1/3o ocean model

11. Submitted proposals regarding HiGEM • VOCALS (T. Toniazzo) • Polar lows (K. Hodges) • Decadal variability (Rowan Sutton’s NERC post-doc) • NCEO: HiGEM-NUGEM model-to-satellite simulators (ISCCP-Calypso-CloudSat-EarthCARE), under the aegis of CFMIP-II; • Exploring a consortium to study weather and climate extremes (with Edinburgh, Oxford)

12. Gaps in science • WWBs -> ENSO • Ocean heat uptake • mixed layer • overturning and heat transport • Sea ice • Precipitation excess, latent heat, radiation • MJO • Initialisation (ocean and sea-ice) • Vertical mixing in the ocean (1.1 vs. 1.2) • Regionalisation of impacts

13. The SST improvement mystery

14. Other activities • Nature and impacts of tropical cyclones: • Multi-scale model intercomparison with Japanese groups (PLV, JS) • Development of TC proxies for low-res GCMs (JS, PLV) • Willis cat modelling (J. Strachan) • Ocean Physics developments (Ian Stevens) • 1%/yr CO2 transient simulation ? • SSTs and Indian monsoon teleconnections in N216 AMIP (G. Martin) • NAO in HiGEM_1.1 (A. Scaife, S. Keeley) • Seasonal prediction (S. Keeley) • Coupling of tropical convection and precip (G. Yang) • MJO (P. Inness)

15. Outlook for HiGEM1-NUGEM • Priority areas: • Ocean-atmosphere (e.g. TC-ocean interaction) • Climate change • Ensembles • Regionalisation of impacts • We will need to base decisions on: • UJCC+HiGEM science • HadGEM3 configuration • Practice in other climate modelling groups • HECToR / Earth Simulator 2 / Reading BG resources Building HiGEM2

16. Progression of UK Climate Models UKMO NWP resolution until end of 2006 J. Slingo/PLV Atmospheric component resolution costs: physics costs not included ∆x = 270 km ∆x = 135 km ∆x = 90 km ∆x = 60 km Model built for Earth Simulator work 1000s years Runs on a PC 10s years Requires major supercomputer Resolution increase = more CPU / shorter simulation