Net deposition of water vapor on hygroscopic aerosols in saturated or near-saturated marine environments leads to fog, which is defined as an air layer contiguous the ocean surface laden with water droplets and characterized by visibility less than 1 km. A myriad of dynamic, thermodynamic and physicochemical factors affects the growth of fog droplets that are embedded in the smallest (Kolmogorov) scale of turbulence. Straining motions within Kolmogorov eddies limit the droplet growth, possibly leading to an equilibrium radius of fog droplets on the order of several microns. Conversely, associated random motions, advection by larger eddies and gravitational settling in unison influence droplet collisions and coalescence to produce larger droplets. This presentation deals with the growth, maturation and dissipation (i.e., life cycle) of fog in turbulent environments, in particular, the role of small-scale turbulence of marine atmospheric boundary layer. Comprehensive microphysical, turbulence, and meteorological measurements made during the field programs of the ‘Fog and Turbulence Interactions in the Marine Atmosphere (Fatima)’ mega project conducted in the Grand Banks area of North Atlantic and Eastern Yellow Sea, respectively, in the summers of 2022 and 2023, will be outlined. The measurement platforms were instrumented in unprecedented proportions by dozens of investigators, with novel and conventional instruments that probed from ~ 1000 km synoptic to ~ 100 nm microphysical scales of the atmosphere, the upper ~ 250 m of ocean, as well as air-sea fluxes. Novel instruments and instrument systems were developed to probe the smallest scales of turbulence. The processes involved in marine fog genesis are diverse and complicated, and a rate limiting step of fog formation appears to be governed by larger scales [of turbulence] that supply kinetic energy and scalar fluctuations to microscales, which can be parameterized using their respective dissipation rates. Examples will be given to illustrate the role of larger scales in fog formation educed using a number of Fatima field cases.
Joseph Fernando is currently the Wayne and Diana Murdy Endowed Professor of Engineering and Geosciences at University of Notre Dame. He received his education at the University of Sri Lanka (BS), the Johns Hopkins University (MA, PhD) and was a post-doctoral fellow at California Institute of Technology. He is a Fellow of the American Society of Mechanical Engineers, American Physical Society, American Meteorological Society, American Association for the Advancement of Science, American Geophysical Union and International Association of Hydro-Environmental Research and Engineering (IAHR). He was elected to the European Academy in 2009. He received docteur honoris causa form University of Grenoble, France, in 2014 and Doctor of Laws Honoris Causa from University of Dundee, Scotland in 2016. He is the Editor-in-Chief of the Journal of Environmental Fluid Dynamics and an Editor of the journals Theoretical and Computational Fluid Dynamics and Journal of Non-Linear Processes in Geophysics and an Associate Editor of the Proceedings of the Royal Society (London). He has published more than 360 papers spanning some sixty international archival Journals, covering basic fluid dynamics, experimental methods, oceanography, atmospheric sciences, environmental sciences and engineering, air pollution, alternative energy sources, acoustics, heat transfer and hydraulics and fluids engineering. He is/was a Principal Investigator of many international field experiments, including MATERHORN, PERDIGAO, CASPER, ASIRI, ASIRI-RAWI, MISO-BOB, IFFExO, C-FOG, Fatima, ASTRAL and CROCUS projects. (https://efmlab.nd.edu/)
