Atmospheric haze

This air light term contributes to the reduced visibility we call atmospheric haze. 

Atmospheric haze is the condition of reduced visibility caused by the presence of fine particles or NO2 in the atmosphere. The particles must be 0.1-1.0 ptm in diameter, the size range in which light scattering occurs. The source of these particles may be natural or anthropogenic. 

Atmospheric haze has been observed in both the western and eastern portions of the United States. Typical visual ranges in the East are <15 miles and in the Southwest >50 miles. The desire to protect visual air quality in the United States is focused on the national parks in the West. The ability to see vistas over 50-100 km in these locations makes them particularly vulnerable to atmospheric haze. This phenomenon is generally associated with diffuse or widespread atmospheric degradation as opposed to individual plumes. 

ITie major component of atmospheric haze is sulfate particulate matter (particularly ammonium sulfate), along with varying amounts of nitrate particulate matter, which in some areas can equal the sulfate. Other components include graphitic material, fine fly ash, and organic aerosols. 

The secondary source of fine particles in the atmosphere is gas-to-particle conversion processes, considered to be the more important source of particles contributing to atmospheric haze. In gas-to-particle conversion, gaseous molecules become transformed to liquid or solid particles. This phase transformation can occur by three processes absortion, nucleation, and condensation. Absorption is the process by which a gas goes into solution in a liquid phase. Absorption of a specific gas is dependent on the solubility of the gas in a particular liquid, e.g., SO2 in liquid H2O droplets. Nucleation and condensation are terms associated with aerosol dynamics. 

Atmospheric haze can occur over regions of several thousand square kUometers, caused by the oxidation of widespread SO2 and NO2 to sulfate and nitrate in relatively slow-moving air masses. In the eastern United States, large air masses associated with slow- moving or stagnating anticyclones have become sufficiently contaminated to be called hazy blobs. These blobs have been tracked by satellites as they develop and move across the country (15). 

The major purpose of ambient particulate sampling is to obtain mass concentration and chemical composition data, preferably as a function of particle diameter. This information is valuable for a variety of problems effects on human health, identification of particulate matter sources, understanding of atmospheric haze, and particle removal processes. 

Particulate emissions have their greatest impact on terrestrial ecosystems in the vicinity of emissions sources. Ecological alterations may be the result of particulate emissions that include toxic elements. Furthermore, the presence of fine particulates may cause light scattering, known as atmospheric haze, reducing visibility and adversely affecting transport safety, property values, and aesthetics. 

Perrin found that, if an emulsion of gamboge were allowed to settle, the granules did not all fall flat to the bottom of the vessel, but remained permanently forming a kind of atmospheric haze extending to a short distance into the liquid. The suspended particles were seen under the microscope to be in Brownian motion. 

Chemical radicals—such as hydroxyl, peroxyhydroxyl, and various alkyl and aryl species—have either been observed in laboratory studies or have been postulated as photochemical reaction intermediates. Atmospheric photochemical reactions also result in the formation of finely divided suspended particles (secondary aerosols), which create atmospheric haze. Their chemical content is enriched with sulfates (from sulfur dioxide), nitrates (from nitrogen dioxide, nitric oxide, and peroxyacylnitrates), ammonium (from ammonia), chloride (from sea salt), water, and oxygenated, sulfiirated, and nitrated organic compounds (from chemical combination of ozone and oxygen with hydrocarbon, sulfur oxide, and nitrogen oxide fragments). ... 

Methods for the direct and continual measurement of chemicals in the particles of the atmospheric haze that are known to be formed during photochemical-pollution episodes and are already suspect as respiratory irritants . By implementing such measurements, it will be possible to find out to what extent the occurrence of such substances can be reduced by various emission controls. To assess actual population expo-... 

Atmospheric Effects. The presence of fine particles (0.1-1.0 mm in diameter) or N02 in the atmosphere can result in atmospheric haze or reduced visibility due to light scattering by the particles. The major effect of atmospheric haze has been degradation in visual air quality and is of particular concern in areas of scenic beauty, including most of the major national parks such as Great Smoky Mountain, Grand Canyon, Yosemite, and Zion Parks. 

Atmospheric particles are produced in virtually all combustion processes and are also formed when volatile products of plant origin are irradiated in the presence of a light-absorbing species such as NO2. The bluish atmospheric hazes common in forested mountainous areas have been attributed to the latter process. Traces of SOj also promote the formation of organic particulate material. These particles, entering the atmosphere, are the principal locus for PAHs. 

Weather condition No precipitation, no fog or atmospheric haze, no strong gust or storm... 

The second category of pictorial cues is strongly coupled to the perceived spatial frequency (texture density gradient, blur from defocus) and color/luminance (atmospheric haze, shading). Therefore, these cues are directly processed on a low neuronal level in the HVS (see Sect. 3). 

A color-dependent cue arises from atmospheric haze. For large distances of several kilometers, the contrast of a viewed object decreases due to atmospheric scattering of light by floating particles (see Fig. 21). The human visual system takes this effect into account for an ordinal layering of the visible objects [76]. Additionally, Troscianko et al. have found evidence that saturation gradients are able to convey depth information in a similar fashion as texture gradients [77]. 

Fig. 21 Example of atmospheric haze showing contrast attenuation due to scattering of light by atmospheric particles. Thus, more distant hills are rendered desaturated and with less contrast...

The human visual system extracts depth information from various physical effects which manifest as pictorial depth cues. One of these effects is atmospheric haze which has been discussed in Sect. 7.2 of chapter Human Visual Perception . Furthermore, the findings of Troscianko et al. [37] indicate that depth encoded in color (de-)saturation influences human depth perception in general. These results point towards a subconscious interpretation of relative color saturation in the viewed image. This effect is associated with the weak ordinal depth cues which support the assessment of scene layering and foreground/background separation process (see Sect. 5.2 of chapter Human Visual Perception ). 

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