LDEO Climate Modeling Group

THE CLIMATE MODELING and Diagnostics Group at the Lamont-Doherty Earth Observatory (LDEO) of the Earth Institute at Columbia University includes more than 200 researchers studying the origin, evolution, and future of the natural world. The Climate Modeling Group carries out research in climate modeling and climate change, also taking into account important issues in the phenomenon of global warming, such as El Nino/Southern Oscillation. Climate Group builds on the data produced from general circulation models (GCMs) to answer fundamental science questions.

LDEO is developing several climate models. The Lamont Ocean-AML GCM (LOAM) is a recent recreation of the Gent-Cane Primitive Equation Ocean Model with many supplementary elements. It was developed for modeling the equatorial Pacific on a stretched longitude/latitude A-grid. Most of the horizontal features have been kept in the present version. The fourth order time and space (horizontal) discretization has been retained, the Shapiro filters (reduced, conservative, narrow passage modifications) are still used, and most of the old options remain. The only major exception is that the reduced-gravity setup (assuming no motion at depth) is not currently supported in this version, but could be reintroduced. The major changes from the original Gent/Cane model are the vastly improved I/O handling, a barotropic solver, a new ocean mixed-layer parameterization and an atmospheric mixed layer (AML).

The Coupler for the Atmosphere with Multi Element LOAM (CAMEL) was partly funded by the Lamont-Doherty Earth Observatory Investment Fund (LIF). The underlying idea of this project is to create a simple tool to combine atmosphere, land, ocean, and sea-ice models. CAMEL interpolates the surface fluxes computed in the atmosphere model to land, ocean, and sea-ice models. It also interpolates the surface temperature computed in these models to the atmosphere model.

The models can be kept as separate exécutables and the communication is done by reading/writing netCDF files. The interpolations and scheduling is all done by CAMEL, with the separate models waiting for updated information. If any of the components are already coupled into one model, as in CCM3(atmosphere) and LSM (land), then CAMEL does not interfere, but does the coupling only between separate models. More generally, CAMEL can be used to patch together the surface conditions of multiple models. In addition, in any geographic area, climatological surface conditions may be combined with model output.

The Climate Model Data Documentation Project (CMDDP) was born of the need to analyze model data to support the scientific conclusions. This raised [Page 598]problems regarding archiving, accessibility, and documentation of the group's results, and relating to the integrity and reproducibility of the group's modeling experiments. Typically, the published data of modelers consists of figures, processed data, and tables of area averaged, depth-integrated, time-smoothed data. Due primarily to size constraints, the computer output is not available for further analysis. In addition, the source code for the models themselves is not easily reproduced. Even scientists based at the same institutions who repeat a model run frequently report different results from some unknown combination of code evolution, change in personnel, migration of computer platforms and data storage, or lack of proper documentation of parameters. To address this problem, which risks compromising the scientific effort, the Climate Modeling Group launched a comprehensive, web-based procedure for ensuring the integrity of local GCM runs. Data can be supplied over the internet through the Distributed Océanographie Data System (DODS) to the whole community. In addition, all necessary documentation, source code, and initialization and forcing data can be stored in one place. The creation and maintenance of this Climate Model Data Documentation Project has achieved a new standard for this type of research. All new published modeling results in the group will be added to this project. Existing projects will also be added to this effort.

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