Atmospheric modeling in the Climate System

Joe Tribbia

NCAR.ESSL.CGD.AMP

The climate represents a coupled system

consisting of an atmosphere, hydrosphere,

biosphere, and cryosphere

What is CCSM?

Coupler(CPL7)

Atmosphere(CAM3->4)

Ocean(POP)

Sea Ice(CICE4)

Land(CLM3)

Aerosols

Trop ChemAerosols

Strat ChemWACCM

Isotopes

(H,C,O)

Isotopes

(H,C,O) DynamicVegetation

Isotopes

(H,C,O)

BioGeochemistry

BioGeochemistry

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 exchangebetween other model components)

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)

Time LoopDynamics

Shallow Convection

Moist Deep

Convection

Dry Adiabatic Lapse

Rate Adjustment

Boundary Layer

Processes

Coupling to land/ocean/ice

Chemistry

Radiation

Stratiform Clouds,

Wet Chemistry,

Aerosols

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 andused in the practicum

Examples of Global Model Resolution

Typical Climate Application Next Generation Climate Applications

Vertical resolution

Resolution near sfc 100m

Resolution near tropopause is >

1000m

Variable placement

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

High-Resolution Global Modeling is ValuableBut

Courtesy, NASA Goddard Space Flight Center Scientific Visualization Studio

Reference Panel

Still a Need to Treat Subgrid-Scale Processes

zoom T42

Grid

Galapagos

Islands

Panama

~ 130 km

Mesoscale -5/3 spectrumNastrom –Gage spectrum

Observations

The value of resolution

T370 (~30km) almost there Spectral Element (~15km)

n.b. compensated spectrum

o Deep Convection+ Updraft Ensemble+ Downdraft Ensemble+ Closure+ Numerical Approximations+ Deep Convective Tracer Transport

o Shallow/Middle Tropospheric Moist Convectiono Evaporation of convective precipitationo Prognostic Condensate and Precipitation Parameterization

+ Macroscale component+ Microphysics component

o Dry Adiabatic Adjustmento Parameterization of Cloud Fraction

What is in moist 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

What is in SW and LW radiation physics?

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

What is in Surface fluxes and Turbulence?

Dynamics-Physics InterfaceConsider a prognostic equation for ψ (a generic variable)

Process Split (Spectral) Time Split (FV)

Physics={Moist, Radiation, Surface, Turbulence} symbolically

n.b. ORDER MATTERS !

gotten from iteration of

IN OPERATOR FORM

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

Some examples of Model Applications

• IPCC Integrations of 20th Century –attribution of warming to anthropogenic forcing

• Coupled ENSO predictions

• Gauging the predictability of decadal climate variability

Natural

1000 1200 1400 1600 1800 2000

Volcanism

Solar

IPCC: CLIMATE FORCINGS

Crowley, T.J., Causes of

Climate Change Over the

Past 1000 Years, Science,

289 270-277, 2000.

Atmospheric modeling in the Climate System

Joe Tribbia

NCAR.ESSL.CGD.AMP

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

Calibrate with 20th century and test anthropogenic impact

Some ENSO results 1year prediction

2yr Enso prediction

Decadal PredictabilityMOC in 20th Century Ensemble Integrations

PI CONTROL

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

Parametric sensitivity in CAMc0 (autoconversion rate)

CAM change interaction consequences

Precip changes in DJF Stationary waves at 300 hPa

Climate results for coupled system

Revised/Dilute Standard/Undilute

JJA FV 2x2.5 1979-1988

Modifications to CAM Convectionby Neale & Mapes

Observationally based

Dilute

Undilute

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

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)

The End

physpkg.F90

cam_comp.F90

tphysbc.F90

tphysacF90