Community Atmosphere Model

Community Atmosphere Model
Name	Community Atmosphere Model
Developer	National Center for Atmospheric Research
Released	0 2003
Latest release version	CAM6
Latest release date	2018
Programming language	Fortran
Operating system	Unix-like
Platform	High-performance computing
Genre	Climate model
Website	https://www.cesm.ucar.edu/models/cam/

Community Atmosphere Model. The Community Atmosphere Model is a comprehensive numerical model of the Earth's atmosphere used for simulating climate and weather phenomena. Developed and maintained by the National Center for Atmospheric Research, it serves as the atmospheric component of the widely used Community Earth System Model. The model is a cornerstone of modern climate science, providing critical data for the Intergovernmental Panel on Climate Change assessment reports and advancing understanding of atmospheric chemistry, cloud physics, and planetary boundary layer processes.

Overview

The Community Atmosphere Model is a sophisticated general circulation model designed to represent the complex physical and dynamical processes of the planetary atmosphere. It operates on a three-dimensional computational grid spanning the globe from the Earth's surface to the stratosphere, solving the fundamental equations of fluid dynamics and thermodynamics. The model's primary purpose is to project future climate change under various greenhouse gas emission scenarios, contributing essential data to major international scientific assessments like those conducted for the Paris Agreement. Its simulations are integral to research published in leading journals such as the Journal of Climate and Geophysical Research Letters.

Development and history

The origins of the Community Atmosphere Model trace back to the Atmospheric Model Intercomparison Project and earlier modeling efforts at the National Center for Atmospheric Research in Boulder, Colorado. Its development was significantly advanced through collaborations with the U.S. Department of Energy and institutions like the University Corporation for Atmospheric Research. Key figures in its early development included scientists such as Warren Washington and Akira Kasahara. The model's first official version was released in 2003, building upon the legacy of the NCAR Community Climate Model and incorporating advancements from field campaigns like the Atmospheric Radiation Measurement program.

Model components and structure

The architecture of the Community Atmosphere Model consists of several interconnected physical parameterization schemes. These include modules for cloud microphysics based on work by scientists like William R. Cotton, a radiation scheme handling interactions with solar irradiance and greenhouse gases, and a land surface model for simulating exchanges with vegetation and soil moisture. The dynamical core, which solves the primitive equations, has evolved through versions employing spectral, finite-volume, and high-order methods. The model also incorporates detailed representations of aerosol species, atmospheric chemistry for compounds like ozone and methane, and sophisticated treatments of turbulence within the planetary boundary layer.

Applications and scientific contributions

The Community Atmosphere Model has been deployed in major international research initiatives including the Coupled Model Intercomparison Project, which feeds directly into reports by the Intergovernmental Panel on Climate Change. Its simulations have been crucial for studying phenomena such as the Madden-Julian oscillation, changes in Arctic sea ice, and the dynamics of the Asian monsoon. Research using the model has provided key insights into climate sensitivity, the role of anthropogenic aerosols in global dimming, and potential future shifts in extreme weather events like hurricanes and heat waves. Findings have influenced policy discussions at forums like the United Nations Framework Convention on Climate Change.

Versions and evolution

The model has undergone significant evolution since its inception, with major version releases denoted as CAM3, CAM4, CAM5, and the current CAM6. Each iteration introduced major scientific advancements; for example, CAM4 improved the representation of deep convection, while CAM5 incorporated a more sophisticated aerosol module. The development process is highly collaborative, involving the CESM Working Groups and the broader community of researchers at institutions like the Massachusetts Institute of Technology and the Lawrence Livermore National Laboratory. The transition to CAM6 featured enhanced resolution options and improved physics for cloud-aerosol interactions.

Relationship to the Earth System Model

The Community Atmosphere Model is fundamentally designed as the atmospheric component of the Community Earth System Model, a fully coupled model that also includes the Community Land Model, the Parallel Ocean Program, and the Community Ice Code for sea ice. Within this framework, it exchanges data on fluxes of heat, water vapor, and momentum with the ocean model and the land surface model at each model time step. This coupling is essential for simulating complex feedback mechanisms, such as those between Arctic amplification and ocean circulation, studied in projects like the Energy Exascale Earth System Model sponsored by the U.S. Department of Energy.

Category:Climate modeling Category:Atmospheric dynamics Category:Scientific simulation software