Microphysics and Optical Attenuation in Fog: Observations from Two Coastal Sites
Tóm tắt
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.
Tài liệu tham khảo
Arnon S, Barry J, Karagiannidis G, Schober R, Uysal R (2012) Advanced optical wireless communication systems. Cambridge University Press
American Meteorological Society (2020) Fog. Glossary of meteorology. http://glossary.ametsoc.org/wiki/fog
Bohren CF, Huffman DR (1983) Absorption and scattering of light by small particles. Wiley, New York
Bouchet O, Sizun H, Boisrobert C, de Fornel F, Favennec PN (2006) Free-space optics propagation and communication, 1st edn. ISTE, London
Clark PA, Harcourt SA, Macpherson B, Mathison CT, Cusack S, Naylor M (2008) Prediction of visibility and aerosol within the operational Met Office Unified Model. I: model formulation and variational assimilation. Q J R Meteorol Soc 134:1801–1816
Daniels ZD (2019) Quantifying HEL weapon system performance in a coastal fog environment. MS thesis, The Naval Postgraduate School
Demers F, Yanikomeroglu H, St-Hilaire M (2011) A survey of opportunities for free space optics in next generation cellular networks. The Ninth Annual Communication Networks and Services Research Conference (CNSR), Ottawa, ON, 2011, pp. 210-216
Duthon P, Colomb M, Bernardin F (2019) Light transmission in fog: the influence of wavelength on the extinction coefficient. Appl Sci 9:2843
Fernando HJS et al (2021) C-FOG: life of coastal fog. Bull Am Meteorol Soc 102:e244–e272. https://doi.org/10.1175/BAMS-D-19-0070.1
Gultepe I, Milbrandt JA (2007) Microphysical observations and mesoscale model simulation of a warm fog case during FRAM Project. Pure Appl Geophys 164:1161–1178
Gultepe I, Milbrandt JA (2010) Probabilistic parametrizations of visibility using observations of rain precipitation rate, relative humidity, and visibility. J Appl Meteorol Climatol 49:36–46
Gultepe I, Miller MD, Boybeyi Z (2006) A new visibility parametrization for warm fog applications in numerical weather prediction models. J Appl Meteorol 45:1469–1480
Gultepe I, Pearson G, Milbrandt JA, Hansen B, Platnick S, Taylor P, Gordon M, Oakley JP, Cober SJ (2009) The fog remote sensing and modelling field project. Bull Am Meteorol Soc 90:341–359
Gultepe I et al (2021) A review of coastal fog microphysics during C-FOG. Bound-Layer Meteorol (this issue)
Hansen JE, Travis LD (1974) Light scattering in planetary atmospheres. Space Sci Rev 14:527–610
IAPWS (1997) Release on the refractive index of ordinary water substance as a function of wavelength, temperature and pressure. The International Association for the Properties of Water and Steam (IAPWS), Erlangen, Germany, September 1997 (7 pages). http://www.iapws.org
Isaac K, McArthur B, Korevaar E (2001) Comparison of laser beam propagation at 785 nm and 1550 nm in fog and haze for optical wireless communications. In: Proceedings of SPIE 4214, Optical Wireless Communications III, 6 February 2001. https://doi.org/10.1117/12.417512
Kim M, Lee K, Lee LY (2020) Visibility data assimilation and prediction using an observation network in South Korea. Pure Appl Geophys 177(2):1125–1141. https://doi.org/10.1007/s00024-019-02288-z
Kunkel BA (1981) Comparison of fog drop size spectra measured by light scattering and impaction techniques. Air Force Geophysics Laboratory, AFGL-TR-81-0049, AD A100252, Hanscom AFB, 38 pp. https://apps.dtic.mil/sti/pdfs/ADA100252.pdf
Kunkel BA (1984) Parametrization of droplet terminal velocity and extinction coefficient in fog models. J Clim Appl Meteorol 23:34–41
Meyer MB, Jiusto JE, Lala GG (1980) Measurements of visual range and radiation-fog (haze) microphysics. J Atmos Sci 37:622–629
Muhammad SS, Flecker B, Leitgeb E, Gebhart M (2007) Characterization of fog attenuation in terrestrial free space optical links. Opt Eng 46(6):066001. https://doi.org/10.1117/1.2749502
Peng Y, Lohmann U, Leaitch R, Banic C, Couture M (2002) The cloud albedo-cloud droplet effective radius relationship for clean and polluted clouds from RACE and FIRE.ACE. J Geophys Res. https://doi.org/10.1029/2000JD000281
Petty GW (2004) A first course in atmospheric radiation. Sundog Publishing, ISBN 0-9729033-0-5
Reid JS, Hobbs PV, Rangno AL, Hegg DA (1999) Relationships between cloud droplet effective radius, liquid water content, and droplet concentration for warm clouds in Brazil embedded in biomass smoke. J Geophys Res 104(D6):6145–6153. https://doi.org/10.1029/1998JD200119
Schaarsberg MA (2021) Water and steam refractive index (https://www.mathworks.com/matlabcentral/fileexchange/46179-water-and-steam-refractive-index). MATLAB Central File Exchange. Retrieved March 25, 2021
Stoelinga MT, Warner TT (1999) Nonhydrostatic, mesobeta-scale model simulations of cloud ceiling and visibility for an east coast winter precipitation event. J Appl Meteorol 38(4):385–404