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A total of 15 fog events from two field campaigns are investigated: the High Energy Laser in Fog (HELFOG) project (central California) and the Toward Improving Coastal Fog Prediction (C-FOG) project (Ferryland Newfoundland). Nearly identical sensors were used in both projects to sample fog droplet-size spectra, wind, turbulence, and thermodynamic properties near the surface. Concurrent measurements of visibility were made by the present weather detector in both experiments, with the addition of a two-ended transmissometer in the HELFOG campaign. The analyses focused first on contrasting the observed fog microphysics and the associated thermodynamics from fog events in the two locations. The optical attenuation by fog was investigated using three methods: (1) derived from Mie theory using the measured droplet-size distribution, (2) parametrized as a function of fog liquid water content, and (3) parametrized in terms of total fog droplet number concentration. The consistency of these methods was investigated. The HELFOG data result in an empirical relationship between the meteorological range and liquid water content. Validation of such relationship is problematic using the C-FOG data due to the presence of rain and other factors. The parametrization with droplet number concentration only does not provide a robust visibility calculation since it cannot represent the effects of droplet size on visibility. Finally, a preliminary analysis of the mixed fog/rain case is presented to illustrate the nature of the problem to promote future research. [ABSTRACT FROM AUTHOR]

The goal of this work is to summarize synoptic meteorological conditions during the Coastal Fog (C-FOG) field project that took place onshore and offshore of the Avalon Peninsula, Newfoundland, from 25 August until 8 October 2018. Visibility was measured at three locations at the Ferryland supersite that are about 1 km from each other, and at two additional sites 66 and 76 km to the north. Supporting meteorological measurements included surface winds, air temperature, humidity, pressure, radiation, cloud-base height, and atmospheric thermodynamic profiles from radiosonde soundings. Statistics are presented for surface measurements during fog events including turbulence kinetic energy, net longwave radiation, visibility, and precipitation. Eleven fog events are observed at Ferryland. Each significant fog event is related to a large-scale cyclonic system. The longest fog event is due to interaction of a northern deep low and a tropical cyclone. Fog occurrence is also examined across Atlantic Canada by including Sable Island, Yarmouth, Halifax, and Sydney. It is concluded that at Ferryland, all significant fog events occur under a cyclonic system while at Sable Island all significant fog events occur under both cyclonic and anticyclonic systems. The fog-formation mechanism involves cloud lowering and stratus broadening or only stratus broadening for the cyclonic systems while for the anticyclonic systems it is stratus broadening or radiation. Although widely cited as the main cause of fog in Atlantic Canada, advection fog is not found to be the primary or sole fog type in the events examined. [ABSTRACT FROM AUTHOR]

The objective of C-FOG (Toward Improving Coastal Fog Prediction) is to advance understanding of fog formation, development, and dissipation over coastal environments to improve fog predictability. The field campaign was taken place over Eastern Canada (Nova Scotia, NS and the Island of Newfoundland, NL) coastlines and open water environments during August-October of 2018 where environmental conditions are known to play an important role for late season's fog formation. Visibility (Vis) and 3D-wind (Uw) are the most critical weather- related parameters affecting marine transportation and aviation operations over sea platforms. During C-FOG field campaign, observations obtained from ground based in-situ, remote sensing, airborne (e.g., balloons) and shipborne platforms as well as data from numerical models were collected. Instruments were located at a supersite (Ferryland, NL) and four satellite sites, as well as on the research vessel Hughes R. Sharp. The instruments measured Uw and turbulence, microphysics, radiation, aerosol, and thermodynamic properties of the fog environment and their profiles. Special sensors were developed for fog microphysics investigation, including a Gondola carrying microphysical sensors such as CDP (Cloud droplet probe) and BCP (backscatter cloud probe) for droplet size range from 1-75 micron. A LPM (laser precipitation monitor) from 100 micron to mm size ranges and an OPC (optical particle counter) above 0.3 micron at 20 spectral channels provided information for fog and drizzle discrimination. Remote sensing platforms (e.g. microwave radiometer, ceilometer, lidar), meteorological towers, tethered balloons, and GOES-R products (e.g. fog coverage and droplet size) provided fog information over horizontal and vertical directions. Preliminary results suggest that fog microphysical parameterizations are related to dynamical processes such as strong moisture advection, turbulent mixing, and ocean surface conditions. The outcome of this project will be used to improve numerical model predictions of fog and develop new microphysical parameterizations applicable marine environments. Overall, C-FOG measurements will be used to evaluate prediction challenges related to fog microphysics, dynamics, and aerosols properties. This research was funded by the Office of Naval Research Award # N00014-18-1-2472 entitled: Toward Improving Coastal Fog Prediction (C-FOG). [ABSTRACT FROM AUTHOR]