Preprints
https://doi.org/10.5194/acp-2021-344
https://doi.org/10.5194/acp-2021-344

  28 Jun 2021

28 Jun 2021

Review status: this preprint is currently under review for the journal ACP.

Surface deposition of marine fog and its treatment in the WRF model

Peter Allan Taylor1, Zheqi Chen1, Li Cheng1, Soudeh Afsharian1, Wensong Weng1, George A. Isaac1,2, Terry W. Bullock3, and Yongsheng Chen1 Peter Allan Taylor et al.
  • 1Centre for Research in Earth and Space Science, Lassonde School of Engineering, York University, Toronto, Ontario, M3J 1P3, Canada
  • 2Weather Impacts Consulting Incorporated, 20 Pine Ridge Trail, Barrie, Ontario, L4M 4Y8, Canada
  • 3Met-Ocean & Digital Environment Solutions, 133 Crosbie Road, St. John’s, NL, A1B 4A5, Canada

Abstract. There have been many studies of marine fog, some using WRF and other models. Several model studies report over-predictions of near surface liquid water content (Qc) leading to visibility estimates that are too low. This study has found the same. One possible cause of this overestimation could be the treatment of a surface deposition rate of fog droplets at the underlying water surface. Most models, including the Advanced Research Weather Research and Forecasting (WRF-ARW) Model, available from the National Center for Atmospheric Research (NCAR), take account of gravitational settling of cloud droplets throughout the domain and at the surface. However, there should be an additional deposition as turbulence causes fog droplets to collide and coalesce with the water surface. A water surface, or any wet surface, can then be an effective sink for fog water droplets. This process can be parameterized as an additional deposition velocity with a model that could be based on a roughness length for water droplets, z0c, that may be significantly larger than the roughness length for water vapour, z0q. This can be implemented in WRF either as a variant of the Katata scheme for deposition to vegetation, or via direct modifications in boundary-layer modules.

Peter Allan Taylor et al.

Status: open (until 09 Aug 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-344', Anton Beljaars, 01 Jul 2021 reply
    • AC2: 'Reply on RC1', Peter A. Taylor, 17 Jul 2021 reply
  • RC2: 'Comment on acp-2021-344', Thierry Bergot, 06 Jul 2021 reply
    • AC1: 'Reply on RC2', Peter A. Taylor, 14 Jul 2021 reply
      • RC3: 'Reply on AC1', Thierry Bergot, 15 Jul 2021 reply

Peter Allan Taylor et al.

Peter Allan Taylor et al.

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Short summary
In marine fog, droplets will impact the water surface, collide and coalesce. This removal process is underestimated or ignored in many fog and weather forecast models. A new atmospheric boundary layer approach is proposed and tested in a standard weather forecast model (WRF). New profile measurements through marine fog layers are suggested.
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