Atmospheric modeling in the Climate System. Joe Tribbia NCAR.ESSL.CGD.AMP

Transcription

1 Atmospheric modeling in the Climate System Joe Tribbia NCAR.ESSL.CGD.AMP

2 The climate represents a coupled system consisting of an atmosphere, hydrosphere, biosphere, and cryosphere

3 What is CCSM? Bio Geochemistry Strat Chem WACCM Isotopes (H,C,O) Atmosphere (CAM3->4) Aerosols Trop Chem Aerosols Ocean (POP) Coupler (CPL7) Sea Ice (CICE4) Isotopes (H,C,O) Land (CLM3) Isotopes (H,C,O) Dynamic Vegetation Bio Geochemistry

4 Some comments on CCSM configurations All components can be interactive All components can be replaced with data models Information about that component is prescribed --- read in from an external dataset CAM can be run with Full interaction As a Chemical Transport Model (acts as a processor and conduit for exchange between other model components)

5 Implementation Details in the atmosphere of possible interest to the class Model performs sequential applications of a number of physical processes State variables (temperature, winds, density, water substances, trace constituents) are updated after each process representation is applied Within CAM processes are divided into two classes Dynamics (the equations of motion = Compressible Navier Stokes equations simplified to hydrostatic balance in the vertical, aka Hydrostatic Primitive Equations) Dynamics = dynamical core = instantaneous solution requires information in latitude, longitude, and height! Physics (diabatic processes such as radiative transfer, processes involving water phase change, chemistry, etc) Physics = parameterizations = solutions typically only require information in height = work on a column by column basis Transport (sometimes)

6 Time Loop Dynamics Dry Adiabatic Lapse Rate Adjustment Chemistry Moist Deep Convection Shallow Convection Stratiform Clouds, Wet Chemistry, Aerosols Boundary Layer Processes Radiation Coupling to land/ocean/ice

7 CAM dynamical cores available for use Spectral dynamics, semi-lagrangian transport (SLT) for tracers --- Traditional Spherical harmonic discretization in horizontal Low order finite differences in vertical Inconsistent, Non-conservative -> fixers required for tracers Semi-Lagrangian Dynamics, semi-lagrangian Transport for tracers Polynomial representation of evolution of mixing ratios for all fields Inconsistent, Non-conservative -> fixers required for tracers Finite Volume (FV) using flux form semi-lagrangian framework of Lin and Rood Semi-consistent, fully conservative Lat-long and cubed sphere gridding Spectral Element (HOMME) with SLT Local polynomial Galerkin discretization Cubed sphere gridding (approximate parallel version of spectral ) Standard and used in the practicum

8 Examples of Global Model Resolution Typical Climate Application Next Generation Climate Applications

9 Vertical resolution Resolution near tropopause is > 1000m Variable placement Resolution near sfc 100m

10 Standard Resolutions Spectral and Semi-Lagrangian dynamics (~2.8x2.8 degree) 26 layers from surface to 35km (optional ~4x4 resolution (T31) through ~0.5x0.5) Finite Volume (2x2.5 degree) 26 layers from surface to 35km (optional 4x5 resolution through 1x1.25) (optional WACCM surface to 150km) Half Atmosphere version (to 70km) Advanced version with 31 layers

11 High-Resolution Global Modeling is Valuable But Still a Need to Treat Subgrid-Scale Processes Panama zoom T42 Grid ~ 130 km Galapagos Islands Reference Panel Courtesy, NASA Goddard Space Flight Center Scientific Visualization Studio

12 Mesoscale -5/3 spectrum Nastrom Gage spectrum Observations

13 The value of resolution T370 (~30km) almost there Spectral Element (~15km) n.b. compensated spectrum

14 What is in moist physics? o Deep Convection + Updraft Ensemble + Downdraft Ensemble + Closure + Numerical Approximations + Deep Convective Tracer Transport o Shallow/Middle Tropospheric Moist Convection o Evaporation of convective precipitation o Prognostic Condensate and Precipitation Parameterization + Macroscale component + Microphysics component o Dry Adiabatic Adjustment o Parameterization of Cloud Fraction

15 What is in SW and LW radiation physics? o Parameterization of Shortwave Radiation + Diurnal cycle + Formulation of shortwave solution + Aerosol properties and optics + Cloud Optical Properties + Cloud vertical overlap + delta-eddington solution + Computation of shortwave fluxes and heating rates o Parameterization of Longwave Radiation + Major absorber and water vapor + Trace gas parameterizations + Mixing ratio of trace gases + Cloud emissivity + Numerical algorithms and cloud overlap

16 What is in Surface fluxes and Turbulence? o Surface Exchange Formulations + Land - Roughness lengths and zero-plane displacement - Monin-Obukhov similarity theory + Ocean + Sea Ice o Vertical Diffusion and Boundary Layer Processes + Free atmosphere turbulent diffusivities + ``Non-local'' atmospheric boundary layer scheme

17 Dynamics-Physics Interface Consider a prognostic equation for ψ (a generic variable) Process Split (Spectral) Time Split (FV) gotten from iteration of IN OPERATOR FORM Physics={Moist, Radiation, Surface, Turbulence} symbolically n.b. ORDER MATTERS!

18 What can you do with these models/tools? Use them as our most comprehensive statement of the earth s climate system to explore the behavior of the system, E.g.: IPCC Assessments of Climate Change Interpreting & understanding the climate record Predicting climate variability Assimilate observations into usable analyses Attempt to improve the representation of component processes within this tool Leads to a better understanding of the component processes Leads to a better understanding of the interactions between processes and system behavior

19 Some examples of Model Applications IPCC Integrations of 20 th Century attribution of warming to anthropogenic forcing Coupled ENSO predictions Gauging the predictability of decadal climate variability

20 IPCC: CLIMATE FORCINGS Volcanism Atmospheric modeling in the Climate Solar System Joe Tribbia NCAR.ESSL.CGD.AMP Natural Crowley, T.J., Causes of Climate Change Over the Past 1000 Years, Science, , 2000.

21 IPCC: CLIMATE FORCINGS Anthropogenic Greenhouse Gases Industrial Aerosols Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001

22 Calibrate with 20 th century and test anthropogenic impact

23 Some ENSO results 1year prediction

24 2yr Enso prediction

25 Decadal Predictability MOC in 20 th Century Ensemble Integrations PI CONTROL

26 Some examples of Exploration of component processes and their interactions Sensitivity of CAM simulation to land/sea discrimination in convection How coupling to Ocean Model changes climate How our formulation of convection influences the climate syste

27 Parametric sensitivity in CAM c 0 (autoconversion rate)

28 CAM change interaction consequences Precip changes in DJF Stationary waves at 300 hpa

29 Climate results for coupled system

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31 Revised/Dilute Modifications to CAM Convection by Neale & Mapes Standard/Undilute Observationally based JJA FV 2x

32 Dilute Undilute

33 Basic Version (what you will run) This is the standard version of cam3.5 - Rasch-Kristjansson (RK) microphysics - CAMRT NCAR Radiation - Bulk Aerosol Model (BAM) prescribed - Holtslag-Boville (HB) PBL and Hack shallow cumulus - Lin-Rood FV dynamical core on lat-long grid - Neale-Richter convection mods and GWD(Fr) changes

34 Advanced (you may hear about) everything ready in September 2008 Advanced mods from Basic: - Morison-Gettelman (MG) microphysics (II) - RRTM AER radiation code (III) - UW PBL/Shallow Cumulus (Bretherton+ Park) - UW Macrophysics (Park) (IV) - Modal Aerosol Model (MAM) prognostic + AEROCOM emission (V)

35 The End physpkg.f90 cam_comp.f90 tphysbc.f90 tphysacf90