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Did you know?: A single column model (SCM) can be an easy, quick, and cheap way to test new or updated physics schemes

Autumn 2017

A SCM replaces advection from a dynamical core with forcing that approximates how the atmospheric column state changes due to large-scale horizontal winds. An atmospheric physics suite then calculates impacts to radiation, convection, microphysics, vertical diffusion and other physical processes as the forcing alters the column state.

The SCM approach is conceptually simple, extremely quick to run (less than a minute on a laptop), and makes interpretation of results less ambiguous because it eliminates three-dimensional dynamical core feedbacks. It can also be relatively straightforward to compare how different physics respond to identical forcing and to perhaps provide evidence or justification for more expensive three-dimensional modeling tests.

The DTC’s Global Model Test Bed (GMTB) project built an SCM on top of the operational Global Forecast System (GFS) physics suite and used it as part of a physics test harness. It can be considered the simplest tier within a hierarchy of physics testing methods. Recently, it has been used to compare how the operational GFS suite performs compared to one with an advanced convective parameterization for simulations of maritime and continental deep convection.

The SCM code is available to collaborators on NOAA's VLab, and will be updated periodically to keep pace with changes in the operational FV3-GFS model. Additionally, as the Common Community Physics Package comes online in the near future, the SCM will be compatible with all physics within that framework.