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Flexible Radiation Codes for Numerical Weather Prediction Across Space and Time Scales

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We seek to develop radiation parameterizations for Navy models that are computationally efficient and work seamlessly across models at all time and space scales, especially from regional models to global models. We are adapting radiation codes developed for climate models for use in the Navy s global weather forecast model NOGAPSNAVGEM, with the possiblity of also introducing them into the limited area model COAMPS. Our long-term goal is to develop codes that are scale-aware, computationally efficient across a range of computer architectures, and operate continuously rather than at discrete time steps. We are developing radiation codes known as PSrad which are modeled on the RRTMG parametization Mlawer et al. 1997 Iacono et al. 2008. We make use of the RRTMG descirption of gas optics, which is among the most accurate parameterizations available Oreopoulos et al. 2012 and initially make many of the same algorithmic decisions, including the choice to neglect longwave scattering. Our codes are intended as a drop-in replacement for RRTMG which has already been implemented in NOGAPS but we have implemented it almost entirely from scratch of the original code, only the subroutine that computes longwave gas optical properties remains. The most important technical difference lies in the organization each of our subroutines is designed to operate on many columns at a time, a choice that increases computational efficiency on a wide range of platforms. Operational centers such as the European Centre for Medium-Range Weather Forecasts have often modified RRTMG in this way Morcrette et al. 2008.

Subject Categories:

  • Meteorology
  • Numerical Mathematics
  • Computer Programming and Software

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