Propagation Effects Handbook for Satellite Systems - DESCANSO ...

Plots of noise temperature and attenuation statistics, both
full-year and quarter-year, are available for the 15 regions at 15
frequencies (8.5, 10, 12, 15, 18, 20, 25, 28, 30, 32, 35, 39, 44, 49
and 90 GHz). Interested persons should contact Stephen Slobin, Jet
Propulsion Laboratory, Pasadena, CA 91109.
6.4.3 ~
6.4.3.1 Water Content of Foq. Fog results from the condensation of
atmospheric water vapor into water droplets that remain suspended in
air. Fog is characterized by optical visibility, which is defined
- as the distance over which a black target against the sky horizon
background can just be discerned by the human eye. The
international definition of fog is satisfied when visibility is less
than one kilometer (Koester and Kosowsky-1970).
There are two main types of fog, differing in the locale and
method of formation. Advection foq is coastal fog that forms when
warml moist air moves over colder water. The liquid water content
of advection fog does not normally exceed 0.4 g/m3. Radiation fog
forms inland at night, usually in valleys and low marshes, and along
rivers. Radiation fog can have a liquid water content up to 1 g/m3.
Empirical relations have been found (Koester and Kosowsky-1970)
between the liquid water content,pt, and the visibility, V(km):
pt = (18.35 V)-1.43 for advection fog (6.4-2)
pc = (42.0 V)-1.54 for radiation fog (6.4-3)
6.4.3.2 Attenuation of Foq. The specific attenuation of fog (in
dB/km) is estimated using the curves in Figure 6.4-1. The 10°C curve
is recommended for the summer, and the O°C curve should be used for
other seasons. Typical liquid water content values for both types
of fog vary between about 0.1 and 0.2 g/m3. The specific attenuation
of this, assuming a temperature of 10°, would be about 0.08 to 0.16
dB/km at 35 GHz, or 0.45 to 0.9 dB/km at 95 GHz. (See Figure 6.4-
1.) In a typical fog layer 50 m thick, a path at a 30° elevation
angle would be in the fog only 100 m, producing less than 0.1 dB of
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