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Meteorological Aspects of Air Pollution
Published in Subhash Verma, Varinder S. Kanwar, Siby John, Environmental Engineering, 2022
Subhash Verma, Varinder S. Kanwar, Siby John
This type of inversion usually occurs at night and results from the normal diurnal cooling cycle. After sunset, the ground loses heat by radiation and cools the air in contact with it. Consequently, a temperature inversion is set up in the first few hundred metres above the surface between the cool low-level air and the warmer air above. If the air is moist and its temperature is below the dew point, fog will form. This type of inversion is more common in winter than summer because of the longer nights. However, the next morning, the sunlight will destroy the inversion as the earth is warmed.
Meteorology
Published in David House, Seamanship Techniques, 2019
Fog is defined as visible water vapour at the earth’s surface. Mist may be similarly defined, except that mist tends not to impede navigation to the same degree as fog. A state of fog exists when visibility is less than 1,000 m (914.4 m). Where visibility falls below 200m it is considered hazardous to surface navigation.
Satellite Transmission Impairments
Published in Jerry D. Gibson, The Communications Handbook, 2018
Fog results from the condensation of atmospheric water vapor into droplets that remain suspended in air. There are two types of fog: advection fog, which forms in coastal areas when warm, moist air moves over colder water, and radiation fog, which forms at night, usually in valleys, low areas, and along rivers. Typical fog layers are only 50-100 m in height, and, hence, the extent of fog on a slant path is very small, even for low elevation angles. Fog attenuations are much less than 1 dB for frequencies up to 100 GHz. A prediction model, developed by Altshuler, is available for the estimation of fog attenuation for frequencies above 30 GHz [Altshuler, 1984 rev. 1986].
Vision improvement system using image processing technique for adverse weather condition of opencast mines
Published in International Journal of Mining, Reclamation and Environment, 2019
Debashis Chatterjee, S. K. Chaulya
Fog is created by minute water droplets floating in air. It scatters light which as a result human visibility is reduced as discussed in Koschmieder’s Law [12]. During day time, two effects are combined:Figure 2Inherent luminance of any object decreases exponentially with the distance to the observer, Figure 2 illustrates the principle of dispersion of light by daytime fog. The radiance R resembles to I0, the direct transmission is the first term of the Equation (1) and the airlight is the second tem of this equation.The involvement of the atmospheric luminance rises exponentially with distance
Thermodynamic coupling characteristics in hybrid (dry/wet) cooling system
Published in International Journal of Green Energy, 2018
Hemin Hu, Yuyan Jiang, Chaohong Guo, Zhigang Li
In the cooling tower, the ambient air introduced by the axial fan installed at the outlet of the cooling tower is warmed and humidified by the hot water at the packing, which is expressed as a blue line, A → To with a solid arrow in the enthalpy–humidity chart provided in Figure 1. The air marked by To from the cooling tower is considered saturated moist air, which is remixed with the ambient air across the red line, To–A. According to the enthalpy-humidity chart operating in winter shown in Figure 1(b), the mixing line To–A falls in the supersaturation region compared to the summer operation shown in Figure 1(a). In winter conditions, the fine droplets suspended in the air form fog, i.e., a visible plume.
Practical aspects of meteorology and oceanography for mariners: A guide for the perplexed
Published in Cogent Engineering, 2018
L. C. Aroucha, H. O. Duarte, E. L. Droguett, D. R. A. Veleda
Regarding fog, there are two types: radiation fog and advection fog. The former occurs on the continent and it is not common on the ocean. The latter is the most important at sea. It occurs when a hot and humid air mass moves above a cold sea surface (Koračin et al., 2014). For the possibility of fog formation, SST must be smaller than the dew point temperature (DPT) (i.e. temperature when air reaches saturated conditions), and on sea fog days the DPT is 5ºC greater than days without fog (Kim & Yum, 2010). The probability of fog occurrence increases when the difference between air temperature and DPT is less than 2ºC for coastal and restricted waters navigation and air humidity around 95% (Lobo & Soares, 2007). The presence of fog can be very dangerous for navigation, especially in restricted waters where dangers are closer. Dense fog is responsible for 32% of all accidents at sea worldwide, 40% at the Atlantic (Tremant, 1987). Considering the fact that it occurs on the ocean surface, it difficults visual navigation, reducing mariners visibility (Koračin et al., 2014). According to Lobo and Soares (2007), atmospheric phenomena can reduce visibility to a distance of:Fog: less than 1 km, and in the case of a dense fog, less than 100 m;Rain: 1500 m, however a drizzle can reduce visibility in a larger scale. A strong drizzle, for example, can cause less than 500 m visibility;Mist: humid mist from 1 km to 2 km, and dry mist from 1 km to 5 km.