Inference of fog characteristics from attenuation measurements at millimeter and optical wavelengths

Abstract

Measurements of fog characteristics are rare, and therefore models for predicting the attenuation caused by fog on the propagation of electromagnetic radiation are scarce. Using experimental transmissions through moderate radiation fogs on a 500‐m path, a method is developed to infer the physical characteristics of fog from concurrent attenuation measurements at millimeter, infrared, and visible wavelengths. It makes it possible to retrieve the fog drop size distribution, as well as its time evolution, during the life cycle of a fog event. It yields realistic values for fog features, such as liquid water content and average drop diameter, which are not easily measured. Furthermore, on an experimental basis, simple relationships between inferred fog characteristics and measured attenuation are proposed. It is found that while both millimetric and infrared attenuations are directly related to liquid water content, visible attenuation strongly depends on the size of the fog droplets. Overall, using these relationships together with statistical distributions of inferred fog characteristics enables predictions of fog attenuation at any wavelength from millimetric to visible.

The Multiple Scattering of Laser Beam Propagation in Advection Fog and Radiation Fog

“…Vasseur and Gibbins developed an experimental method to infer the physical characteristics of fog from concurrent attenuation measurements at millimeter, infrared, and visible wavelengths; a gamma function comprised of three parameters is assumed for the drop size distribution. Simulations of fog attenuation based on the inferred drop size distribution are found in excellent agreement with the measurements [16]. Al Naboulsi et al investigated laser system performance in the advection and convection fog in the 0.4 μm to 15 μm spectral zone, the author also proposes a fast transmission relations based on an exact Mie theory calculation valid in the 0.69 μm to 1.55 μm spectral bands [17].…”

“…Te dimensions of fog droplets are much greater the visible optical wavelength, so Q e (r) of fog droplets can be consider as 2 [17]. c can be written as follows [16]:…”

C-FOG: Life of Coastal Fog

“…The signal only began spiking to readable levels after 1800 UTC 29 September, even though the Battery PWD was no longer consistently reporting fog from 1100 UTC 29 September. In all, a scintillometer could prove to be a useful tool for determining spatial characteristics of fog, as alluded to by Vasseur and Gibbins (1996).…”

Review of weather impact on outdoor terahertz wireless communication links

“…(2) Advection fog forms in coastal regions throughout the day when warm moist air moves over colder water by advection. For radiation fog, its water content ranges from 0.01 to 0.1 g/m 3 with diameter of water droplets smaller than 20 [47]. Diameters for advection fog can be near 20 with water content being higher than 0.2 g/m 3 .…”