**Model Information of Potential Use to the IPCC Lead Authors and the
AR4.**

**Parallel Climate Model (PCM)**

20 April 2005

**I. Model identity:**

A. Institution, sponsoring agency, country

> Parallel Climate Model (PCM)
>
> National Center for Atmospheric Research (NCAR),
>
> NSF (a primary sponsor), DOE (a primary sponsor), NASA, and NOAA
>
> USA

B. Model name (and names of component atmospheric, ocean, sea ice, etc.
models)

> Coupled model Parallel Climate Model (PCM)
>
> Atmosphere Community Climate Model
>
> Ocean Parallel Ocean Program,
>
> Sea ice Community Sea Ice Model
>
> Land Land Surface Model (LSM)

C. Vintage (i.e., year that model version was first used in a published
application)

First control run: Aug 1998

D. General published references and web pages

Main website : <http://www.cgd.ucar.edu/pcm>

> general model description and initial 1% CO2 increase results:
>
> Washington, W.M., J.W. Weatherly, G.A. Meehl, A.J. Semtner Jr., T.W.
> Bettge, A.P. Craig, W.G. Strand Jr., J.M. Arblaster, V.B. Wayland, R.
> James, Y. Zhang, 2000: Parallel climate model (PCM) control and
> transient simulations. Clim. Dyn., 16, 755\--774.
>
> documentation of El Nino well-simulated in PCM:
>
> Meehl, G.A., P. Gent, J.M. Arblaster, B. Otto-Bliesner, E. Brady, and
> A. Craig, 2001: Factors that affect amplitude of El Nino in global
> coupled climate models. Clim. Dyn., 17, 515\--526.
>
> documentation of the recent IPCC climate change results from PCM (and
> CCSM3):
>
> Meehl, G.A., W.M. Washington, W.D. Collins, J.M. Arblaster, A. Hu,
> L.E. Buja, W.G. Strand, and H. Teng, 2005a: How much more global
> warming and sea level rise? Science, 307, 1769\--1772.
>
> Regarding CCSM3 documentation of the IPCC runs, there is a paper under
> review in J. Climate with that information. I attach a pre-print. The
> reference:
>
> Meehl, G.A., W.M. Washington, B.D. Santer, W.D. Collins, J.M.
> Arblaster, A. Hu, D. Lawrence, H. Teng, L.E. Buja, and W.G.Strand,
> 2005: Climate change in the 20th and 21st centuries and climate change
> commitment in the CCSM3. J. Climate, submitted.

E. References that document changes over the last \~5 years (i.e., since
the IPCC TAR) in the coupled model or its components. We are
specifically looking for references that document changes in some
aspect(s) of model performance.

> documentation of the 20th century forcing experiments with PCM
> (forcings include volcanoes, solar, GHGs, sulfate aerosols, ozone):
>
> Meehl, G.A., W.M. Washington, C. Ammann, J.M. Arblaster, T.M.L.
> Wigley, and C. Tebaldi, 2004: Combinations of natural and
> anthropogenic forcings and 20th century climate. J. Climate, 17,
> 3721\--3727.

F. IPCC model version\'s global climate sensitivity (KW-1m2) to increase
in CO2 and how it was determined (slab ocean expt., transient
expt\--Gregory method, =B12K Cess expt., etc.)

G. Contacts (name and email addresses), as appropriate, for:

1\. coupled model: Lawrence Buja, <southern@ucar.edu>

2\. atmosphere: Lawrence Buja, <southern@ucar.edu>

3\. ocean: Lawrence Buja, <southern@ucar.edu>

4\. sea ice: Lawrence Buja, <southern@ucar.edu>

5\. land surface: Lawrence Buja, <southern@ucar.edu>

6\. vegetation: Lawrence Buja, <southern@ucar.edu>

7\. other: Lawrence Buja, <southern@ucar.edu>

IPCC runs: Lawrence Buja, <southern@ucar.edu>

**II. Besides atmosphere, ocean, sea ice, and prescription of
land/vegetated surface, what can be included (interactively) and was it
active in the model version that produced output stored in the PCMDI
database?**

A. atmospheric chemistry?

B. interactive biogeochemistry?

No

C. what aerosols and are indirect effects modeled?

No indirect forcing effects are included.

D. dynamic vegetation?

No

E. ice-sheets?

No

**III. List the community based projects (e.g., AMIP, C4MIP, PMIP,
PILPS, etc.) that your modeling group has participated in and indicate
if your model results from each project should carry over to the current
(IPCC) version of your model in the PCMDI database.**

**IV. Component model characteristics (of current IPCC model version):**

A. Atmosphere

1\. resolution

> Lateral resolution from 42-wavenumber triangular spectral truncation
> of the dynamics. At the equator, the spatial resolution is
> approximately 2.8 degrees.

2\. numerical scheme/grid (advective and time-stepping schemes; model
top; vertical coordinate and number of layers above 200 hPa and below
850 hPa)

Numerical scheme Eulerian spectral transform,

> Grid: T42
>
> Time stepping: semi-implicit leapfrog
>
> Model top: 2.2 hPa
>
> Vertical coordinate: generalized terrain-following hybrid coordinate,
>
> 26 levels
>
> Number of layers above 200 hPa: 13
>
> Number of layers below 850 hPa: 4

3\. list of prognostic variables (be sure to include, as appropriate,
liquid water, chemical species, ice, etc.)

> a\. Vorticity
>
> b\. Divergence
>
> c\. Temperature
>
> d\. Specific humidity
>
> e\. Surface pressure
>
> f\. Grid box averaged liquid condensate amount
>
> g\. Grid box averaged ice condensate amount

4\. name, terse descriptions, and references (journal articles, web
pages) for all major parameterizations. Include, as appropriate,
descriptions of:

a\. clouds

b\. convection

> Shallow convection:
>
> Hack, J. J., Parameterization of moist convection in the National
> Center for Atmospheric Research Community Climate Model (CCM2), J.
> Geophys. Res., 99, 5551-5568, 1994.

c\. boundary layer

> Non-local atmospheric boundary layer scheme
>
> Holtslag, A. A. M., and B. A. Boville, Local versus nonlocal
> boundary-layer diffusion in a global climate model, J. Climate, 6,
> 1825-1842, 1993.

d\. SW, LW radiation

> LW: absorptivity-emissivity method for clear-skies, plus Truncated
> Independent Column Approximation (TICA) for all-sky
>
> SW: delta-Eddington with exponential-sum fit representation of
> near-IR, truncated ICA (TICA) for all-sky
>
> Kiehl, J. T., J. J. Hack, G. B. Bonan, B. B. Boville, D. L.
> Williamson, and P. J. Rasch, The National Center for Atmospheric
> Research Community Climate Model: CCM3, J. Climate, 11, 1131-1149,
> 1998.

e\. any special handling of wind and temperature at top of model

> Horizontal diffusion of temperature and wind with a del-squared
> diffusion operator is introduced in the top three layers of the model.

B. Ocean

1\. resolution

nominal 1 degree displaced pole horizontal grid

320x384 horizontal grid points

40 vertical levels

1.125degx0.27deg resolution on the equator

northern pole in Greenland

2\. numerical scheme/grid, including advection scheme, time-stepping
scheme, vertical coordinate, free surface or rigid lid, virtual salt
flux or freshwater flux

third-order upwinding advection

3-time-level second-order modified leapfrog time stepping

40-level geopotential grid extending to 5500m,

with resolution increasing from 10m at the surface to 250m

in the deep ocean.

implicit free surface

virtual salt flux

3\. list of prognostic variables and tracers

grid-oriented zonal and meridional velocity components

vertical velocity

pressure

density

potential temperature

salinity

ideal age

4\. name, terse descriptions, and references (journal articles, web
pages) for all parameterizations. Include, as appropriate, descriptions
of:

a\. eddy parameterization

b\. bottom boundary layer treatment and/or sill overflow treatment

None

c\. mixed-layer treatment

> KPP boundary layer mixing
>
> Large, W.G., J.C. McWilliams and S.C. Doney, 1994: Oceanic vertical
> mixing: A review and a model with a nonlocal boundary layer
> parameterization, Reviews of Geophysics, 32, 363-403.

e\. tidal mixing

None

f\. river mouth mixing

g\. mixing isolated seas with the ocean

h\. treatment of North Pole \"singularity\" (filtering, pole rotation,
artificial island?)

C. sea ice

1\. horizontal resolution, number of layers, number of thickness
categories

> gx1v3 grid (nominally 1 degree, displaced pole grid. see ocean
> resolution)

2\. numerical scheme/grid, including advection scheme, time-stepping
scheme,

3\. list of prognostic variables

4\. completeness (dynamics? rheology? leads? snow treatment on sea ice)

> dynamics: elastic-viscous-plastic (Hunke and Dukowicz, 1997) with
> updates (Hunke, 2001; Hunke and Dukowicz, 2002; Hunke and Dukowicz,
> 2003)

5\. treatment of salinity in ice

6\. brine rejection treatment

7\. treatment of the North Pole \"singularity\" (filtering, pole
rotation, artificial island?)

D. land / ice sheets (some of the following may be omitted if
information is clearly included in cited references.

1\. resolution (tiling?), number of layers for heat and water

2\. treatment of frozen soil and permafrost

3\. treatment of surface runoff and river routing scheme

4\. treatment of snow cover on land

5\. description of water storage model and drainage

6\. surface albedo scheme

7\. vegetation treatment (canopy?)

8\. list of prognostic variables

9\. ice sheet characteristics (How are snow cover, ice melting, ice
accumulation, ice dynamics handled? How are the heat and water fluxes
handled when the ice sheet is melting?)

E. coupling details

1\. frequency of coupling

> ocean coupled once per day, atm/lnd/ice coupled once per hour

2\. Are heat and water conserved by coupling scheme?

> yes

3\. list of variables passed between components:

a\. atmosphere - ocean

b\. atmosphere - land

c\. land - ocean

d\. sea ice - ocean

e\. sea ice - atmosphere

4\. Flux adjustment? (heat?, water?, momentum?, annual?, monthly?).

> none

**V. Simulation Details (report separately for each IPCC simulation
contributed to database at PCMDI):**

A. IPCC \"experiment\" name

B. Describe method used to obtain initial conditions for each component
model

1\. If initialized from a control run, which month/year.

2\. For control runs, describe spin-up procedure.

C. For pre-industrial and present-day control runs, describe radiative
forcing agents (e.g., non-anthropogenic aerosols, solar variability)
present Provide references or web pages containing further information
as to the distribution and temporal changes in these agents.

D. For perturbation runs, describe radiative forcing agents (e.g., which
greenhouse gases, which aerosols, ozone, land surface changes, etc.)
present. Provide references or web pages containing further information
as to the distribution and temporal changes in these agents.