CM2.1 Climate Model
This is a combination atmospheric circulation (AM2-Finite
Volume at 2 degree resolution, 24 vertical layers), ocean circulation (MOM4 at 1
degree resolution, 50 vertical layers), Land hydrology (LAD) and
simple river routing that is the current ESMDT development
workhorse that was development by the Coupled Model Development
Team headed by Delworth, Stouffer and Rosati to be used in IPCC climate studies. This model is formulated
from a subset of the models below, all of which are coded in the
Flexible Modeling System infrastructure.
Atmospheric Circulation
The AM2 structure uses a hybrid vertical coordinate that
includes both pressure and terrain-following (i.e. sigma)
layers. Its "physical core" (i.e. vertical
parameterizations for physical processes) includes formulation of radiation, specific
humidity and the effects of clouds. Development of these
models is coordinated through the Global Atmospheric
Model Development Team, and comes in two varieties of
"dynamical core" (i.e. horizontal parameterizations of
advection and diffusion):
- B-grid: In this formulation of dynamics, momentum (u,v) points are co-located, but
staggered from pressure and tracer points on
the Arakawa b-grid, a description of which can be
found HERE.
-
Finite Volume: This effort is headed by S. J. Lin. In this formulation of dynamics, the horizontal discretization is based on a
conservative, flux-form, semi-Lagrangian scheme
described by Lin and Rood [Mon. Wea. Rev., 124, 2046-2070, 1996.] and Lin
and Rood [Q. J. R. Meteorol. Soc., 123, 2531-2533, 1997].
A description can be
found HERE.
Atmospheric Chemistry
-
Simple tracer transport: Chemical tracers are transported conservatively through
the atmosphere with only surface fluxes in and out as
source functions.
-
AM2-CHEM: Development of these models is headed by
Horowitz, Ginoux and Fiore and coordinated through the Global Atmospheric
Model Development Team. This model includes on-line gas-phase and aerosol
chemistry. Emissions, chemistry and deposition are based upon the
MOZART-2 model [Horowitz et al., 2003; Tie et al., 2004] that are
fully documented HERE).
The current version of AM2-CHEM includes NOx-ozone-CO-hydrocarbon and
aerosol (sulfate, nitrate, carbonaceous, dust) chemistry, consisting of
70 chemical species and 167 chemical and photochemical reactions.
Ocean Circulation
Development of these models is headed by
Griffies and Hallberg and coordinated through the Ocean
Model Development Team.
-
Modular Ocean Model, Version 4
(MOM4): This effort is headed by Griffies. MOM4 is a z-coordinate, volume-conserving model with
parameterizations of a free surface, explicit water
fluxes, orientation of horizontal
diffusion along isopycnal contours (i.e. neutral physics), Gent-McWilliams
thickness diffusion, KPP mixed layer, partial cells,
multi-dimensional flux limiting advection and other
features fully documented HERE.
-
Hallberg Isopycnal Model in Fortran (HIMF)This effort is headed by Hallberg. The plan is to convert ocean
biogeochemistry into this code once a coupled atm-ocean
model is developed with HIM.
Ocean Biogeochemistry/Ecology
Development of these models headed by
Dunne, Slater and Sarmiento
and coordinated through the Earth System
Model Development Team:
-
OCMIP2 Biotic: Includes ocmip2 biotic suite of
biogeochemical tracers (DIC, ALK, PO4, DOP, O2) forced with surface
restoring of PO4 to an observed climatology. Specifically, the
model takes climatological fields from the World
Ocean Atlas 2001 (PO4) and the
Carbon
Dioxide Information Analysis Center (DIC and ALK)
databases and rescales them to follow
OCMIP2
protocols, which are strictly adhered to.
-
Restoring Biogeochemistry: Includes an extended suite of
biogeochemical tracers (DIC, ALK, NO3, NH4, PO4, SiO4, ALK, Fed, DON,
DOP, LDOC, O2) forced with surface restoring of PO4, NO3 and SiO4
to the observed monthly climatology from the World
Ocean Atlas 2001 (NO3, PO4, SiO4) and the
Carbon
Dioxide Information Analysis Center (DIC, ALK) databases and a surface
Fed climatology of J. Dunne after Johnson and Archer (1997).
Food web processing
in the euphotic zone and remineralization/dissoltion through the
ocean interior are handled as in Dunne et al. (in prep). The model
includes a treatment of nitrogen fixation/denitrification. Carbon
dioxide equilibria and gas exchange follow OCMIP2
protocols.
-
Tracers for Ocean Phytoplankton with Allometric
Zooplankton (TOPAZ) Biogeochemistry: Includes an explicit ecological model
including three phytoplankton groups (small, large/diatoms and
diazotrophs), growth limitation by light, temperature and a suite of
nutrients including nitrate, ammonia, phosphate, iron and silicate,
dissolved inorganic carbon, alkalinity, two kinds of dissolved
organic material, O2, nitrogen fixation and denitrification. CO2
gas exchange is function of the biologically and physically forced
solubility. Additionally, changes in the vertical distribution of
phytoplankton affect heat absorption with climate feedbacks. Food
web processing in the euphotic zone
and remineralization/dissolution through the ocean interior are
handled as in Dunne et al. (in prep). Initialization
of the model takes
initial climatological fields from the World
Ocean Atlas 2001 (NO3, PO4, SiO4) and the
Carbon
Dioxide Information Analysis Center (DIC, ALK) databases. Carbon
dioxide equilibria and gas exchange follow
OCMIP2
protocols.
Land/Soil Hydrology
Development of these models headed by Milly
and coordinated through the Land
Model Development Team (internal access only)
-
LAnd Dynamics (LAD) soil hydrology
model: This is the land model used in CM2 for GFDL's current
physical climate change simulations. It includes a
spatially-variable "bucket" for water storage. Temperature within
soils is vertically-resolved, while temperature in an
overlying snowpack layer (if existant) is assumed to be
fixed. The thermal and latent heat capacity of soil
water is tuned to reproduce diurnal
variability.
-
LAnd Dynamics 2 (LAD2) soil hydrology
model: This effort is ongoing. This is this next generation land model that utilizes a more
physically-motivated representation of snow, soils, and
river storage capacity currently being developed by Chris
Milly. Temperature is vertically resolved in both
snow and soils. The thermal and latent heat capacity of
water is treated explicity (rather than
parameterized). Water storage in soils is handled through
a series of finite-volume vertical layers (rather than the
single bucket concept of LAD).
Land/soil Biogeochemistry/Ecology
Development of these models is headed by
Pacala, Sheviakova and Maleshev and coordinated through the Land
Model Development Team
-
Soil Hydrology and Ecology (SHE) Model: Based on the framework of LAD, this model is capable of simulating the global distribution and functioning of terrestrial carbon sources and sinks as well as the exchange of water and energy between land, vegetation, and atmosphere. The carbon acquired through photosynthesis is balanced by plant respiration and carbon accumulation in leaves, roots, sapwood, and wood. In addition, the model simulates soil carbon pools processes. The land model tracks carbon dynamics of vegetation and soil in response to environmental conditions, ambient concentration of CO2, natural disturbances (e.g. fire), and anthropogenic land use changes (e.g. deforestation and agricultural cropland abandonment). Additionally, changes in the distribution of vegetation structural characteristics affect key land surface parameters such as albedo and surface roughness with climate feedbacks.
-
SHE - LAD2 coupling: This effort is ongoing.
River Routing
Development of these models is headed by
Findell and Milly and coordinated through the Land
Model Development Team
-
Capacitor/transporter Model: Overflow from the soil model empties into a surface/ground
water reservior with a
spatially-variable timescale of loss. This water loss is then
is routed instantaneously through a river network to the
ocean.Chemical tracers are transported conservatively
-
Explicit River system Model: Surface water, ground water and River segments are treated
explicitly with loss rates to the next segment being a
function of the amoount of water in them.
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