Fog Formation Related to Gravity Currents Interacting with Coastal Topography

Stef L. Bardoel, Daniel V. Horna Muñoz, Andrey A. Grachev, Raghavendra Krishnamurthy, Leonardo P. Chamorro, Harindra J.S. Fernando

Research output: Contribution to journalArticlepeer-review

Abstract

An interesting mixing-fog event was identified during the C-FOG field campaign, where a cold-frontal airmass arriving from the north-east collided with The Downs peninsula in Ferryland, Newfoundland, Canada, to produce misty/foggy conditions. A comprehensive set of field observations suggests that this collision caused turbulent mixing of nearly saturated ambient air with an almost saturated cold-frontal airmass, creating conditions for mixing fog. To delve into the physical processes underlying this phenomenon, laboratory experiments were performed on the interaction of lock-exchange-induced gravity currents with a rectangular obstacle. Instantaneous velocity and density fields were obtained using particle image velocimetry and planar laser-induced fluorescence. The observations suggest that the obstacle starts affecting the approaching gravity-current propagation at an upstream distance of 2H and, upon collision, the mixing occurs over a length of 0.83H, where H is the depth of the ambient fluid layer. The time for larger-scale turbulent stirring to permeate to the smallest scales of turbulence and activate the condensation nuclei is estimated as 3 t, where t∗=H/g′ is the intrinsic time scale of the gravity current, and g is the reduced gravity. Extrapolation of laboratory results to field conditions shows a good agreement with observations.

Original languageEnglish (US)
JournalBoundary-Layer Meteorology
DOIs
StateAccepted/In press - 2021

Keywords

  • C-FOG field campaign
  • Gravity currents
  • Mixing fog
  • Topography
  • Turbulent mixing

ASJC Scopus subject areas

  • Atmospheric Science

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