Single Precision in the Dynamical Core of a Nonhydrostatic Global Atmospheric Model: Evaluation Using a Baroclinic Wave Test Case

Single Precision in the Dynamical Core of a Nonhydrostatic Global Atmospheric Model: Evaluation... AbstractReducing the computational cost of weather and climate simulations would lower electric energy consumption. From the standpoint of reducing costs, the use of reduced precision arithmetic has become an active area of research. Here the impact of using single precision arithmetic on simulation accuracy is examined by conducting Jablonowski and Williamson’s baroclinic wave tests using the dynamical core of a global fully compressible nonhydrostatic model. The model employs a finite volume method discretized on an icosahedral grid system and its mesh size is set to 220 km, 56 km, 14 km, and 3.5 km. When double precision arithmetic is fully replaced by single precision arithmetic, a spurious wavenumber-5 structure becomes dominant in both hemispheres, rather than the expected baroclinic wave growth only in the northern hemisphere. It was found that this spurious wave growth comes from errors in the calculation of grid cell geometrics. Therefore we performed an additional simulation using double precision for calculations that only need to be performed for model setup, including calculation of grid cell geometrics, and single precision everywhere else, meaning that all calculations performed each time step used single precision. In this case, the model successfully simulated the growth of the baroclinic wave with only small errors and a 46% reduction in runtime. These results suggest that the use of single precision arithmetic will allow significant reduction of computational costs in next-generation weather and climate simulations using a fully compressible nonhydrostatic global model with the finite volume method. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Monthly Weather Review American Meteorological Society

Single Precision in the Dynamical Core of a Nonhydrostatic Global Atmospheric Model: Evaluation Using a Baroclinic Wave Test Case

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Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0493
D.O.I.
10.1175/MWR-D-17-0257.1
Publisher site
See Article on Publisher Site

Abstract

AbstractReducing the computational cost of weather and climate simulations would lower electric energy consumption. From the standpoint of reducing costs, the use of reduced precision arithmetic has become an active area of research. Here the impact of using single precision arithmetic on simulation accuracy is examined by conducting Jablonowski and Williamson’s baroclinic wave tests using the dynamical core of a global fully compressible nonhydrostatic model. The model employs a finite volume method discretized on an icosahedral grid system and its mesh size is set to 220 km, 56 km, 14 km, and 3.5 km. When double precision arithmetic is fully replaced by single precision arithmetic, a spurious wavenumber-5 structure becomes dominant in both hemispheres, rather than the expected baroclinic wave growth only in the northern hemisphere. It was found that this spurious wave growth comes from errors in the calculation of grid cell geometrics. Therefore we performed an additional simulation using double precision for calculations that only need to be performed for model setup, including calculation of grid cell geometrics, and single precision everywhere else, meaning that all calculations performed each time step used single precision. In this case, the model successfully simulated the growth of the baroclinic wave with only small errors and a 46% reduction in runtime. These results suggest that the use of single precision arithmetic will allow significant reduction of computational costs in next-generation weather and climate simulations using a fully compressible nonhydrostatic global model with the finite volume method.

Journal

Monthly Weather ReviewAmerican Meteorological Society

Published: Jan 5, 2018

References

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