GFDL CM2.X
Encyclopedia
GFDL CM2.X is a coupled atmosphere-ocean general circulation model (AOGCM) developed at the NOAA Geophysical Fluid Dynamics Laboratory
in the United States
. It is one of the leading climate models used in the Fourth Assessment Report of the IPCC
, along with models developed at the Max Planck Institute for Climate Research, the Hadley Centre and the National Center for Atmospheric Research
. The solutions of these GFDL CM2 models are described in a series of papers published in the Journal of Climate in 2006.
The atmospheric component of the CM2.X models is a 24-level atmosphere run at a resolution of 2 degrees in the east-west and 2.5 degrees in the north-south direction. This resolution is sufficient to resolve the large mid-latitude cyclones responsible for weather variability. It is too coarse, however, to resolve processes such as hurricanes or intense thunderstorm outbreaks. The atmosphere
includes a representation of radiative fluxes, mixing in the atmospheric boundary layer, representations of the impacts
of stratus
and cumulus
clouds, a scheme for representing drag on upper level winds caused by gravity waves, changes in
the spatial distribution of ozone, and the ability to represent the impact of multiple greenhouse gasses.
Ocean
The ocean component is a 50 level ocean, run at a resolution of 1 degree in the east-west direction and varying in the north-south direction from 1 degree in the polar regions to 1/3 of a degree along the equator. This resolution is sufficient to resolve the equatorial current system, but is too coarse to capture the highly energetic mesoscale eddies- whose advective and diffusive
effects must be parameterized. Other key parameterizations include
a free surface height which changes in response to evaporation, precipitation, and convergence of ocean currents, absorption
of sunlight tied to observed chlorophyll concentrations, a representation of the oceanic mixed layer
, inclusion of turbulence
generated by tidal mixing on shelves and schemes allowing water from marginal seas such as the Red Sea and Baltic Sea to "mix" across
narrow straits at their mouths.
, with the CM2.0 exhibiting the common bias of winds that are shifted equatorward but the CM2.1 model being one of the few that have winds close to the correct latitude and magnitude in this region (Russell et al., 2006). Work by Reichler and Kim at the University of Utah suggests that this model series is one of the top models in a range of atmospheric characteristics. It also has one of the better simulations of El Nino among the IPCC models (van Oldenburgh et al., 2005; Wittenberg et al., 2006). However, as is the case with most AOGCMs run without flux adjustment, the models fail to capture the cold upwelling zones along the eastern boundaries of the Pacific and Atlantic, and tend to produce an overly dry Amazon basin.
Geophysical Fluid Dynamics Laboratory
The Geophysical Fluid Dynamics Laboratory is a laboratory in the National Oceanic and Atmospheric Administration /Office of Oceanic and Atmospheric Research . The current director is Dr. V...
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. It is one of the leading climate models used in the Fourth Assessment Report of the IPCC
Intergovernmental Panel on Climate Change
The Intergovernmental Panel on Climate Change is a scientific intergovernmental body which provides comprehensive assessments of current scientific, technical and socio-economic information worldwide about the risk of climate change caused by human activity, its potential environmental and...
, along with models developed at the Max Planck Institute for Climate Research, the Hadley Centre and the National Center for Atmospheric Research
National Center for Atmospheric Research
The National Center for Atmospheric Research has multiple facilities, including the I. M. Pei-designed Mesa Laboratory headquarters in Boulder, Colorado. NCAR is managed by the nonprofit University Corporation for Atmospheric Research and sponsored by the National Science Foundation...
. The solutions of these GFDL CM2 models are described in a series of papers published in the Journal of Climate in 2006.
Model construction
AtmosphereThe atmospheric component of the CM2.X models is a 24-level atmosphere run at a resolution of 2 degrees in the east-west and 2.5 degrees in the north-south direction. This resolution is sufficient to resolve the large mid-latitude cyclones responsible for weather variability. It is too coarse, however, to resolve processes such as hurricanes or intense thunderstorm outbreaks. The atmosphere
includes a representation of radiative fluxes, mixing in the atmospheric boundary layer, representations of the impacts
of stratus
Stratus cloud
A stratus cloud is a cloud belonging to a class characterized by horizontal layering with a uniform base, as opposed to convective clouds that are as tall or taller than wide . More specifically, the term stratus is used to describe flat, hazy, featureless clouds of low altitude varying in color...
and cumulus
Cumulus cloud
Cumulus clouds are a type of cloud with noticeable vertical development and clearly defined edges. Cumulus means "heap" or "pile" in Latin. They are often described as "puffy" or "cotton-like" in appearance. Cumulus clouds may appear alone, in lines, or in clusters...
clouds, a scheme for representing drag on upper level winds caused by gravity waves, changes in
the spatial distribution of ozone, and the ability to represent the impact of multiple greenhouse gasses.
Ocean
The ocean component is a 50 level ocean, run at a resolution of 1 degree in the east-west direction and varying in the north-south direction from 1 degree in the polar regions to 1/3 of a degree along the equator. This resolution is sufficient to resolve the equatorial current system, but is too coarse to capture the highly energetic mesoscale eddies- whose advective and diffusive
effects must be parameterized. Other key parameterizations include
a free surface height which changes in response to evaporation, precipitation, and convergence of ocean currents, absorption
of sunlight tied to observed chlorophyll concentrations, a representation of the oceanic mixed layer
Mixed layer
The oceanic or limnological mixed layer is a layer in which active turbulence has homogenized some range of depths. The surface mixed layer is a layer where this turbulence is generated by winds, cooling, or processes such as evaporation or sea ice formation which result in an increase in salinity...
, inclusion of turbulence
generated by tidal mixing on shelves and schemes allowing water from marginal seas such as the Red Sea and Baltic Sea to "mix" across
narrow straits at their mouths.
Simulation description
Two sets of models were run for the IPCC, consisting of very similar ocean circulations but different methodology for solving the equations of motion. The result is that the models have very different wind stresses over the Southern OceanSouthern Ocean
The Southern Ocean comprises the southernmost waters of the World Ocean, generally taken to be south of 60°S latitude and encircling Antarctica. It is usually regarded as the fourth-largest of the five principal oceanic divisions...
, with the CM2.0 exhibiting the common bias of winds that are shifted equatorward but the CM2.1 model being one of the few that have winds close to the correct latitude and magnitude in this region (Russell et al., 2006). Work by Reichler and Kim at the University of Utah suggests that this model series is one of the top models in a range of atmospheric characteristics. It also has one of the better simulations of El Nino among the IPCC models (van Oldenburgh et al., 2005; Wittenberg et al., 2006). However, as is the case with most AOGCMs run without flux adjustment, the models fail to capture the cold upwelling zones along the eastern boundaries of the Pacific and Atlantic, and tend to produce an overly dry Amazon basin.
External links
- http://nomads.gfdl.noaa.gov/CM2.X/ CM2 global climate model info and model output data files from the GFDL Data Portal.
- http://www.gfdl.noaa.gov/research/climate/highlights/ Climate research highlights featuring GFDL CM2 model results. Includes text, graphics and animations.