Joe Fernando
University of Notre Dame
Seminar Information
Engineering Building Unit 2 (EBU2)
Room 479
Seminar Recording Available: Please contact seminar coordinator, Jake Blair at (j1blair@ucsd.edu)
Net deposition of water vapor on hygroscopic aerosols in saturated or near-saturated marine environments leads to marine fog, which is defined as an air layer contiguous the ocean surface laden with water droplets, with 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, dynamics of larger eddies and their influence on smaller eddies as well as 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 on marine-fog lifecycle. Comprehensive microphysical, turbulence, and meteorological measurements 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 in Fatima were instrumented in unprecedented proportions by dozens of investigators. Both novel and conventional instruments so deployed probed across ~ 1000 km synoptic to 1 mm Kolmogorov scales; ~ 0.1-1.0-micron microphysical scales in the atmosphere; turbulence and hydrophysical properties of upper ~ 250 m of the ocean; and variability of air-sea fluxes. The processes involved in marine fog lifecycle 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 identified using a number of Fatima field cases.
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 and 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. He was the lead Principal Investigator of many large international field experiments, most recent being Fatima, C-FOG and Perdigao.