AMWG Meeting

1
Overview of CAM status and simulations

• Bill Collins and Jim Hack
• National Center for Atmospheric Research
• Boulder, Colorado

• Update on model status, simulations, and release
• Computational performance of CAM
• Features of model simulations

2
Topics

• Overview of status and analysis of CAM
• Discussion of new diagnostic efforts
• Discussion of new physics parameterizations
• Update on extensions to model
• Overviews of work on isentropic coordinates by
  other modeling groups
• Open discussion
• Objectives for summer workshop

3
Agenda
4
Developments since June 2001 Workshop

• Conducted first coupled simulations
• Implementation/restructuring
• implementation of new CAM design
• parameterization interface
• creation of constituents module
• addition of new ESMF time-manager
• continued work on splitting dynamics and physics
• incorporated chunking data structures (2D
  decomposition)
• other ongoing implementation changes
• shared constants, file naming conventions, etc.

5
Developments since June 2001 Workshop

• Major modifications/improvements
• Fractional surface specification implemented and
  validated
• works properly for all three dynamical cores
• introduces minor simulation changes
• CSIM ice thermodynamics implemented and validated
• specified and prognostic snow cover implemented
  and evaluated
• slightly colder ice temperatures
• reasonable seasonal cycle in snow cover

6
Developments since June 2001 Workshop

• Numerous minor modifications/improvements
• Minghua Zhang prognostic cloud-water closure
  modification
• vertical diffusion on dry static energy
• update static energy instead of T between
  parameterizations
• modifications required for coupled simulations
• changes to cloud drop number concentration over
  sea ice
• changes to methodology for determining rain vs.
  snow
• other changes required for middle-atmosphere
  configuration
• creation of final boundary datasets
• SST and sea ice concentration

7
Upcoming Papers on CAM

• General overview
• New sea-ice formulation
• Finite volume dynamical core
• Parameterization for statiform fractional
  cloudiness
• New H2O longwave and cloud overlap
• Hydrometeor evaporation mechanism
• New global SST climatology
• Fractional ice and land
• Coupling of parameterizations with dynamical core
• Heating and kinetic energy dissipation
• Tracer transport

8
Release of CAM to Community

• CAM 2.0 and CCSM 2.0 will be released May 17
  (02)
• Contents of release
• Model component source code build and run
  scripts
• Three dynamical cores Eulerian, semi-Lagrange,
  and Finite Volume
• Web-based documentation
• Users Guide (how to run the model)
• Reference Guide (details of the code structure)
• Scientific Guide (description of physics and
  dynamics)
• Initial and boundary data sets
• New SST and sea-ice concentration data
• Model data sets
• AMIP-2 and climatological SST uncoupled
  integrations(Eulerian dynamics)

9
Computational Performance

• Supported platforms
• Compaq
• IBM-SP
• Linux Portland group and Lahey compilers
• SGI
• Sun
• Performance
• 1 month per 32 wall-clock minutes on 32 IBM
  Power3 Pes
• Equivalent to 4 years per wall-clock day on same
  setup
• Reduced grip speed-up 25-30 (Eul. SLD
  uncoupled only)

10
TOA Energy ComponentsFractional Land/Sea Ice vs
Integer Representation
11
Surface Energy ComponentsFractional Land/Sea Ice
vs Integer Representation
12
Surface Energy FluxesFractional Land/Sea Ice vs
Integer Representation
Latent Heat Flux
Precipitation Rate
13
Surface TemperatureCSIM Thermodynamic Ice vs
Old Ice Thermodynamics
14
Surface TemperatureCSIM Thermodynamic Ice vs
Old Ice Thermodynamics
15
New Blended SST-Sea Ice Concentration Data

• Completed in collaboration with CVWG
• blending technique developed by Jim Hurrell
• blends HadISST 1949-1980 with Reynolds 1979-2001
• screening technique to ensure reasonable SST-sea
  ice relationship
• PCMDI procedures for ensuring correctness of time
  interpolation
• extensive quality control procedures
• Fifty-three year dataset (1949-2001)
• can easily be extended as new SST data are
  created by NCEP
• currently have completed 21 year control
  experiment (1979-2000)

16
Southern Oscillation Index
17
Southern Oscillation Index
18
Sea Ice, Snow Height, and Precipitation
RateFractional Land/Sea Ice, CSIM
Thermodynamics, New SST
19
General Simulation Properties/Framework

• Scientifically defensible extendible
  framework
• spectral Eulerian dynamics (reduced-grid capable)
• T42 truncation
• 26 levels
• prognostic cloud water
• generalized cloud overlap (plus requisite changes
  to LW SW)
• updated long wave water vapor absorption
  formulation
• modified deep convection parameterization

20
General Simulation Properties/Framework

• Improvements in several important simulation
  features
• precipitable water
• precipitation distribution
• eastern ocean solar energy budget
• elements of eastern Pacific surface wind stress
• Degradations in simulation features
• colder troposphere, particularly the tropical
  tropopause
• tendency for more zonal double-ITCZ structure
• warm surface temperature bias?

21
Temperature (coupled framework)
22
Surface Temperature (coupled framework)
23
Precipitable Water (coupled framework)
24
Precipitable Water (coupled framework)
25
Precipitation Rate (coupled framework)
26
Surface Stress (coupled framework)
27
Net Longwave Surface Fluxes (coupled)
28
Net Surface Energy Flux (coupled)
29
Surface Temperature (against obs)
30
Eastern Pacific Surface Stress
31
E. Pacific Surface Stress Resolution Dependence?
32
Future Work

• Begin ensemble of 50 year long control
  simulations
• conducted in coordination with Climate
  Variability Working Group
• will serve as the basis for documenting
  simulation characteristics
• Accelerate exploration of alternative dynamical
  frameworks
• T31 paleo configuration (update for fractional
  surface formulation)
• T85 configurations (Eulerian and semi-Lagrangian
  for now)
• continued evaluation of simulations with
  finite-volume dynamical core
• Begin systematic investigation of specific
  simulation biases
• AMWG should identify short list of prioritized
  projects
• eastern ocean upwelling, double ITCZ, cold
  tropopause temps, ...
• climate sensitivity, variability (e.g., MJO), ...
• form teams to develop comprehensive scientific
  plan of attack
• experimental strategy
• diagnostic strategy

33
Future Work

• AMWG research infrastructure
• needs to be able to support research activities
  on multiple fronts
• boundary layer
• dynamical cores
• stratiform clouds
• middle atmosphere (e.g., WACM)
• radiation parameterization alternatives
• cumulus parameterization alternatives
• AMWG diagnostic infrastructure
• needs to continue to grow in scope and complexity
• evaluate model behavior across wide range of time
  scales
• include dominant modes of climate variability in
  standard analysis
• continued involvement of other CCSM working groups