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NUMAC: Description of the Nested Unified Model with Aerosols and Chemistry, and evaluation with KORUS-AQ data
  • +10
  • Ken S Carslaw,
  • Hamish Gordon,
  • Adrian A Hill,
  • Paul R Field,
  • Nathan Luke Abraham,
  • Andreas Beyersdorf,
  • Chelsea Corr-Limoges,
  • Pratapaditya Ghosh,
  • John Hemmings,
  • Anthony C Jones,
  • Claudio Sanchez,
  • Xuemei Wang,
  • Jonathan Wilkinson
Ken S Carslaw
School of Earth and Environment, University of Leeds
Hamish Gordon
Department of Chemical Engineering and Center for Atmospheric Particle Studies, Carnegie Mellon University, School of Earth and Environment, University of Leeds

Corresponding Author:[email protected]

Author Profile
Adrian A Hill
Met Office
Paul R Field
School of Earth and Environment, University of Leeds, Met Office
Nathan Luke Abraham
Yusuf Hamied Department of Chemistry, University of Cambridge, National Center for Atmospheric Science, University of Cambridge
Andreas Beyersdorf
Department of Chemistry & Biochemistry, California State University
Chelsea Corr-Limoges
Department of Biology & Chemistry, Springfield College
Pratapaditya Ghosh
Department of Civil and Environmental Engineering and Center for Atmospheric Particle Studies, Carnegie Mellon University
John Hemmings
Met Office
Anthony C Jones
Met Office
Claudio Sanchez
Met Office
Xuemei Wang
School of Earth and Environment, University of Leeds
Jonathan Wilkinson
Met Office

Abstract

We describe and evaluate a system for regional modeling of atmospheric composition with the Met Office Unified Model (UM), suitable for climate, weather forecasting and air quality applications. In this system, named NUMAC (`Nested UM with Aerosols and Chemistry'), a global model provides boundary conditions for regional models nested within it, using the Met Office's Regional Nesting Suite for multi-scale simulations. The regional models, which can run at convection-permitting or cloud-resolving scales, use the same code as the global model. The system includes double-moment prognostic aerosol microphysics with interactive chemistry of sulfur species, ozone, NOx and CO as in the UK Earth System Model (UKESM). Double-moment prognostic cloud microphysics is optional. To test NUMAC, we compare simulations to surface and aircraft measurements from NASA's KORUS-AQ campaign over South Korea. The performance of the regional model, which we run at 5 km resolution, is similar to the well-evaluated global model when the regional and global models use the same emissions. Most species such as ozone, NOx, OH, or PM2.5 are simulated within a factor of 2 of observations most of the time, though they are biased low compared to sensors in polluted areas (observed surface dry PM2.5 averages 28ugm-3 but we simulate 17ugm-3). Meteorology and clouds are represented satisfactorily. With higher-resolution emissions, many of the low model biases are reduced, but a tuning was required to keep NO concentrations realistic, indicating shortcomings in the chemistry scheme. We demonstrate the potential of NUMAC for studies of aerosol-cloud interactions.
29 Jun 2023Submitted to ESS Open Archive
09 Jul 2023Published in ESS Open Archive