When run in the coupled model the GFDL AM2.1 model ranked as one of the best IPCC AR4 models (Reichler and Kim, 2008, Bull. Amer. Meteor. Soc.). However there were still a number of aspects that clearly needed to be improved. Many of these aspects relate to the simulation of clouds and of moist convection. In addition, there was no serious attempt to simulate the stratosphere in AM2, and there was no aerosol or gas phase chemistry incorporated into the model. AM3 is an amibitious attempt to move the atmospheric model towards a more physically-based simulation of clouds and convection, allowing for the interaction between clouds and natural as well as anthropogenic aerosols, the simulation of stratospheric ozone (including the Antarctic ozone hole), as well as the tropospheric chemistry needed to discuss transcontinental transport of pollutants and global air quality. The model also takes advantage of developments in the finite volume dynamical core, specifically a new grid with the topology of a cube (the "cubed sphere" grid topology) that results in much improved performance on scalable computer architectures and more homogeneous simulations of flow over polar and non-polar regions.

AM3 Highlights

• Cubed-sphere implementation of the finite-volume dynamical core. The Earth is represented as a cube with six rectangular faces. There is no singularity associated with the north and south poles as with the spherical representation.
• Increased vertical resolution in the stratosphere with the uppermost level at about one Pascal.
  
• Deep Convection using Donner et al. (2001) and Wilcox and Donner (2007) with ensemble of deep plumes with mass fluxes and vertical velocities. Simple bulk microphysics. Mesoscale updrafts and downdrafts.
• Shallow convection after Bretherton et al. (2004, Mon. Wea. Rev.) with buoyancy-sorting, entraining-detraining plume and vertical velocity.
• Cloud droplet activation with aerosol interaction after Ming et al. (2006).
• Interactive/predicted aerosols (20 species).
• Interactive troposperic and stratospheric chemistry (85 species).

AM3 Status

Please note that this model is still under development and is not publicly available. At this time we can not anticipate when it might be available. You may want to consider the public release of our AM2.1 model.

Additional Information

A brief history of atmospheric modeling
at GFDL

The AM2 Model

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