High-performance computing for climate modelling

Transcription

1 DEISA-PRACE Symposium, Amsterdam, 12 mai 2009 High-performance computing for climate modelling Sylvie Joussaume CNRS IPSL/ Laboratoire des Sciences du Climat et de l Environnement Saclay, France Coordinator of the EU FP7 I3 «IS-ENES» Infrastructure for the European Network for Earth System Modelling

2 L. Fairhead/CNRS Climate models Strong evolution: More complexity «Earth System Models» Higher resolution ESM ~ 1000 man years From IPCC (1990) To IPCC (2007) ~200 km ~500 km Source: L. Fairhead, LMD/IPSL

3 Observed Global warming Simulations Natural forcings observations Simulations Natural & Anthropogenic forcings

4 IPCC (2007) Emission scenarios A2 CO2 Temperature B1

5 Challenges in climate modelling Mitigation & Adaptation of climate change Until now : Is there an impact of greenhouse gases emissions by human activities on climate? «Mitigation policy» Now main challenge : what will be the time evolution of climate changes at the regional scale to which societies will have to adapt? Models : Understand and Predict

6 Challenges in climate modelling Issues : What will be the regional impacts of climate change, e.g. changes in extreme events? increase model resolution, improve model physics What are the roles of the components of the Earth system? atmosphere-ocean-biosphere-cryosphere carbon cycle, chemistry and aerosols How can we reduce/quantify uncertainties in future climate change? ensemble experiments (statistics and several models) Model benchmarking Are there possible surprises? need long term simulations

7 Increase resolution : need for impact studies precipitation, extreme events, cyclones, impact on ecosystems Account for local features, e.g. topography, land characteristics Today : Forcing a Regional Climate Model or statistical downscaling ~20-50 km ~ 200 km In the future : high-resolution climate models better general circulation, feedbacks Observations HI-CGCM : T106 (~100 km) Mid-CGCM: T42 (~ 240 km) Kimoto et al. (2005)

8 Increase resolution Highly dependent on computing time resolution x 2 (horizontal & vertical) : computing time processor SX8R 100 years = 2,5 yr CPU 1 x1 x55 niveaux 360x180x55 32 proc SX8R 27 days 480 proc Itanium 36 days IPCC 2007 : one simulation : 3 mths computing time h / 40 To data AR5 x processor SX8R 100 years = 15 days CPU 4 proc SX8R 4 days 3,5 x2,5 x19 niveaux 96x72x19

9 Explicit representation of cloud processes is now possible Miura et al, Science 2007 on 320 nodes Sustained 7.7 TFlops BUT very short simulation (weeks)!!

10 water & energy carbon cycle chemistry LAND ATMOSPHERE OCEAN & SEA ICE 1 CO 2 Aerosols & chemistry

11 Observations : Half of CO2 emissions are absorbed by oceans and land With climate change : reduced sinks of carbon IPCC (2007) Interactive carbon cycle Prescribed CO2 concentrations Which emissions/energy policy for which climate?

12 Need for ensemble simulations Multi-model (IPCC : 23 models used) No single formulation, mean model : «best» Multi-experiments : - statistics : initial conditions & formulation uncertainty e.g. ESSENCE project (DEISA) : extreme events (A. Sterl) - Towards «climate prediction» at decadal time scale - International coordinated benchmarking

13 Need for ensemble simulations - international coordinated benchmarks Next IPCC (2013) - «CMIP5» Near term ~(~50 km) Towards «climate prediction Distributed Data base ~ Pbytes WCRP Longer term > 2100 (~150 km)

14 Model resolution x 1000 up to x 10 6 Complexity x 5-10 Ensembles x 10 to 100 Length x 10 GFlops to TeraFlops : Complexity + Time length + some resolution Teraflops sustained Petaflops Exaflops 400 km / 3000 yrs 200 km / 300 yrs 50 km / 10 years 40 km / 3000 years 20 km / 300 years 5 km / 10 years 2 km / 300 years ~10 experiments Reduced noise Extremes, Hurricanes ice sheet melting Uncertainty Climate impacts

15 Towards Massively parallel? Change of numerics : new dynamical cores No singularity at the pole NICAM Atmosphere only! «AQUAPLANET» eg M. Taylor 10-day expt Tanaka ES annual report ( ) NCAR atmosphere 2008

16 «The development of reliable science-based adaptation and mitigation strategies will only be possible through a revolution in regional climate predictions supported by appropriate climate observations and assessment, and the delivery of this information to society. World Modelling Summit, 2008 Ultimate target : 1 km resolution 2020?? Need for a World Climate Research Facility

17 Network of European groups in climate/earth system modeling Launched in 2001 by Guy Brasseur (MOU) Approximately 50 groups from academic, public and industrial world Main focus : discuss strategy to accelerate progress in climate and Earth system modeling and understanding Several EU projects PRISM, ENSEMBLES, METAFOR, COMBINE, IS-ENES, EUCLIPSE Support to PRACE, DEISA2 Organisation : Scientific Board : S. Joussaume, J.C. André, J. Mitchell, T. Palmer, J. Marotzke, R. Budich, A. Navarra, P. Kabat

18 AR4 IPCC AR4 : 16 modelling groups, 23 models In Europe : 7 /23 models UK, France, Germany, Norway IPCC AR5 : Expecting more modelling groups involved + Italy, EC-Earth consortium (Netherlands, Sweden )

19 Developing the modelling infrastructure in Europe IS-ENES FP7 I / coord IPSL/ 20 partners Infrastructure : Earth System Models (6) / Model data + USA Objectives: Integration of the European ESM community ENES strategy, exchange of expertise/training, portal Development of ESMs service on common tools and model components, common evaluation international standards Prepare for high-end simulations interface with PRACE & DEISA2, improve model performance Foster application of ESM simulations for climate change impacts dissemination of model results, interface with decision makers and users

20 ENES interface with PRACE and DEISA2 Participation to the scientific case for PRACE Letters of support PRACE & DEISA2, IS-ENES Prepare for high-performance computing in IS-ENES: - HPC task force : JC André, R. Budich, MA Foujols, A. Navarra - interface with the ENES community Identified as a virtual community in DEISA2 - requirements, update scientific case, benchmarks PRACE : NEMO & ECHAM5, missing coupled bench - improve model performance use different machines and prototypes - prepare future model generation

21 Conclusions Climate change : crucial role of HPC for society challenges World Modelling Summit 2008 need of worldclass computing facilities EU : DEISA & PRACE Need for HPC ecosystem Easy access to different platforms, distributed data access EU : DEISA, EGEE enhance the infrastructure on models and data software access, data access, international standards international protocols for model evaluation and data sharing a challenge at the national / European / International levels