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Why the haze is an important weather factor, part 2 – impact on visibility and light scattering

Capping inversion seen from Pico del Teide

Capping inversion can be easily seen from freestanding mountains, like the Pico del Teide is. Tenerife, Spain.

 

This writing is a continuation of a whole article about the haze as an important weather factor. Previously I have described the basic types of haze and I drew attention to the impact the atmospheric aerosols on human health. Now, in terms of the continuation, I would like to describe the impact of haze on the light scattering in the atmosphere and the visual range.

1. LIGHT SCATTERING IN HAZY ATMOSPHERE

The presence of the haze in the atmosphere impact on the light scattering. Haze makes usually milky white color for the atmosphere (Pic. 1), while against a bright background it will become yellowish, grey or orange-red at the sunrise/sunset (Pic. 2); likewise, against the darker background, it will be light blue (Pic. 3). This is due to the optical effect caused by the haze particles; i.e. the scattering of light by the haze particles. The type and direction of scattering depend critically on the size of the particle (Ackerman, Knox, 2007). The presence of haze is strongly related to the Beer-Lambert Law, described in an earlier article. It means, that as the cloud is further from the observer, its color turns from dark to bluish, when shaded and from yellowish to reddish, when illuminated.

Sky color depend on haze concentration level

Pic. 1 Haze causes a brighter sky color. As aerosol concentration grows the sky colour is fainter (atmo.arizona.edu).

Grey sky colour apearance due to high haze concentration

Pic. 2 The grey sky appearance near the horizon, where on 1 and 2 haze plays the main role on the contrary of the 3rdpicture, where sky being free of haze is bright above the horizon. On 2nd picture, we can see the grey-orange mixture due to the evening approaches.

Haze concentration influence on cloud color

Pic. 3 Haze concentration washes not only a sky color, but also other colors are changed. For example, a color of dark cumulonimbus cloud base appears to look more bluish, even light blue, when the cloud is further. This phenomenon is strongly associated with the Beer-Lambert Law.

Reflected light attenuation in Earth's atmosphere caused by haze concentration

Pic. 4 Reflected light attenuation in Earth’s atmosphere during the hazy condition in case of low level and mid-level clouds (Cu, Sc), where 1 represents shaded and illuminated by Sun cloud at once closer and 2 further. Watch also the illuminated parts of the cloud, which are more orange, when further from the observer. Kobyle, Zawada Hill, Poland.

There are 3 main sources of the particular matter in the terrestrial atmosphere (Kokhanovsky, 2008):
– surface (e.g dust or sea salt),
– gas to particle conversion
– cosmic aerosols

Important is also the orientation and shape of the aerosol particles, which can slightly modify the route of light through the hazy environment. These shapes are different depends on the kind of environment. In an arid environment, like a desert, semi-desert as well as in continental air mass these shapes can be really various and irregular due to local factors. One of these is a local soil composition and thus aerosol source composition, which can vary dramatically from one region to another (Reid et al., 2003). Another factor is the time of atmospheric residence (see details in the previous article) these particles, which for all this tame falls into reactions with other particles suspended in the air. These reactions change a chemical composition, often along with the physical shape of aerosol (Khalizov et. al., 2009). As a result, dust particles often consist of agglomeration of different materials and tend to have more complicated shapes. These particles can contain sharp edges, points, chains or internal voids.
In a wet environment, aerosols interact with ambient water vapor. This process affects their size, shape, chemical composition and consequently their optical properties. The shape of aerosols depends on the relative humidity.  As more water is coated on the surface of the particle, the overall shape would become more spherical, changing the scattering properties. Water is absorbed by the volume of the particle. In effect, the particle changes its shape, size, and optical properties. In a humid environment, where most of the particles have a regular shape i.e. cubic or spherical, the light scattering will be more effective.
Next to the shape, also the size of atmospheric aerosols is important in light scattering. For arid conditions, the main role in the size of aerosols plays the wind, which keeps them suspended for a long time (Hinds, 1999).

Aerosol dust examples

Pic. 5 Example of dust aerosols, typical in an arid environment: a,b – loess; c,d – palagonite; e,f – Saharian dust (Meland, 2011).

As the final, the pivot factor, determining the degree of light scattering and changes of visual range is relative humidity. We can treat a relative humidity somewhat like a “distance” from the dew point, which is a normal fog, and the observer is able to see nothing. Relative humidity says us about the presence of smallish water droplets in the air, which is next absorbed by aerosol particles or causes their coagulation or condensation. This is a strong relationship between relative humidity and light scattering. Depends on the aerosol hygroscopic fraction the increase of light scattering may start from 50% of relative humidity, whereas at about 70% a rapid light scattering changes are observed (Pic. 6).

Light scattering vs relative humidity

Pic. 6 Light scattering vs relative humidity, where: 1 – by ambient aerosols, 2 – by laboratory aerosols (Lundgren, Cooper, 1969).

Basically, there are 2 types of light scattering depends on the illumination source location. This is forward and backward scattering (Pic. 7).
Forward scattering involves a change of radiation less than 90 degrees. In our case, it will refer to the section of the sky being on the same side, where the primary illumination source – the Sun is.
Backward scattering (backscatter) will involve changes of radiation higher than 90 degrees, thus occur on the antisolar section of the sky (Pic. 8).

A general mechanism of light scattering

Pic. 7 A general mechanism of light scattering in the hazy atmosphere (pages.mtu.edu).

The effect of light scattering depends on the size of the particles (Pic. 8). The weakest light scattering occurs for air molecules and the smallest aerosols, which is typical for near-Rayleigh conditions. The most effective scattering occurs for water droplets or extremely dense haze particles suspended in the atmosphere when non-selective scattering plays the main role.

Light scattering dependance of size particles

Pic. 8 The light scattering dependence from the size of the particles (Hackel, 2009).

We used to treat the Earth’s atmosphere as a place of a multitude of simple particles, where each particle is exposed to and also scatters, the light that has already been scattered by other particles (Liou, 2002). This is a multiple scattering, which is accompanied by absorption. A large absorption occurs for mineral, dustlike and water-soluble particles and particularly for soot (Liou, 2002).
We have to take into account also the effects of the angle between the source of illumination and part of the sky observed. This is easy to spot when the cloud layer covers the sky and some clear gaps appear. Then rays of sunlight (crepuscular rays) can be seen from the point of the sky where the Sun is located. What happens under hazy conditions. When big aerosol concentration takes place under a clear sky, the observer is able to spot a very bright area when looking close to the Sun. The sky appears to be darker towards the symmetric point on the sky or antisolar point  (when an observer is above the layered haze) (Pic. 9).  Knowing, that apparent illuminance of the Sun varies from around 10000 Lx at the 10 deg altitude to 129000 Lx at zenith we can simply calculate the illuminance level of the certain regions of the sky (Pic. 10).

Light scattering on the sky under misty conditions Mie scattering percentage

Pic. 9 Light scattering on the sky under misty weather with the strong influence of Mie scattering. The values state a percentage of incident illumination given by Sun (Hackel, 2009).

Light scattering on the sky under misty conditions Mie scattering estimated Lux values

Pic. 10 Light scatterings on the sky under misty weather with the strong influence of Mie scattering. The values correspond to the assumed illumination level in different regions of the sky, shown in Lux in terms of the percentage values of the incident illumination source. The illumination of the Sun at 50 deg altitude is about 87000 lx. The light absorption by mist has been omitted (Hackel, 2009).

Bluish sky under hazy conditions with forward scattering situation Gorlice

Pic. 11 Bluish-white colour of sky under hazy conditions. You can see the border between a forward scattering (on the right) and backward scattering (on the left). The sky looks bluer under backward scattering conditions. GKS Glinik football stadium, Gorlice, Poland.

Bluish sky under hazy conditions with backward scattering situation Gorlice

Pic. 12 The blue colour of the hazy sky under backward scattering conditions. Backward scattered aerosols cause a greyish tint appearance. Sportowa Street, Gorlice, Poland.

Even during the day free of haze in near Rayleigh scattering conditions the light dispersing throughout the blue sphere illuminated by Sun can be described as per below:

  • The brightest area is near the illumination source (Sun or Moon),
  • The darkest area is located on the opposite side of the sky. Its presence above the horizon depends on the location of the Sun. For example, when Sun shines in zenith, then the darkest area of the sky will encircle the sphere at around 40-50 deg altitude. In case as per picture below, the darkest region of the sky is located more or less on the opposite part of the sky at 50 deg altitude.
  • Light areas of the sky are near the horizon due to the thickness of the atmosphere, whilst the brightest part of the near-horizon sky is to be observed on the Sun direction.
Light scattering on the sky during transparent atmosphere conditions percentage

Pic. 13 Light scattering on the sky under clear weather,  where a Rayleigh scattering plays the main role. The values state a percentage of incident illumination given by Sun (Hackel, 2009).

Under a free of haze conditions, the sky brightness (and diffuse sky radiation) is much more various. The brightest area is located obviously near the Sun, and corresponds around 100% of solar illuminance, however, it is not widely developed likewise in misty conditions. Even near the edge of the Sun, the sky is blue, but its color is less pronounced due to close vicinity to the Sun and forward scattering of air molecules. On the contrary of the solar point, the antisolar direction is much less bright; the range of illuminance level corresponds between less than 10% to about 20% of the illuminance of the incident light. Considering it for solar altitude 50 deg (Pic. 11, 12) the incident light level is going to reach 87000 lx, whereas the sky region in antisolar direction should reach the illumination level about 8 – 18000 lx.

Light scattering on the sky during transparent atmosphere conditions estimated Lux values

Pic. 14 Light scattering on the sky under clear weather, where a Rayleigh Scattering plays the main role. The values correspond to the assumed illumination level in different regions of the sky, shown in Lux in terms of the percentage values of the incident illumination source. The illumination of the Sun at 50deg altitude is about 87000 lx (Hackel, 2009).

Colour of sky under transparent atmosphere conditions, Wapienne spa Poland

Pic. 15 The sky color under clear weather conditions. The border between forward and backward scattering is much less pronounced. Moreover, the sky near zenith or the darkest region has a deep blue color. You can compare it with the pic. 11,12 or another example. Wapienne, Poland.

During the free of haze conditions the main role plays air molecules, that scatter light about equally in the forward and backward direction and scatter more blue light than red, hence is the blue sky (Malm, 2016). Due to haze sky appears to be brighter than during the near Rayleigh scattering conditions.

2.  RELATION WITH PLANETARY BOUNDARY LAYER

The planetary boundary layer also known as the atmospheric boundary layer is the lowest part of the atmosphere. Its behaviour is strongly influenced by Earth’s surface on the temperature, moisture, and wind through the turbulent transfer of air mass. As a result of surface friction winds in the planetary boundary layer are weaker than above and tend to blow toward areas of low pressure. The planetary boundary layer reacts for temperature changes quickly so its thickness is various within the day. Usually, the planetary boundary layer reaches from few several meters up to 5 kilometers (above the desert). Above this layer is the “free atmosphere” where the wind is parallel to isobars unlike to inside this layer where is affected by drag over the surface.

Level of planetary boundary layer during the day

Pic. 16 The level of the planetary boundary layer at the midday hours above different kinds of surface (NOAA Earth System Research Laboratory).

The planetary boundary layer behaviour differs between the flat surface and mountainous area, where is more complicated (Pic. 16, 22). There, it usually adjusts to the local latitude. Land roughness influences the wind system. A big role plays also the effect of landcover. Whereas in the valleys is summer on the top can be still wintry weather with snow cover. These factors make the planetary boundary layer more unpredictable. Moreover planetary boundary layer changes throughout the day (Pic. 17) due to changes in irradiation.

The structure of planetary boundary layer

Pic. 17 The structure of the planetary boundary layer throughout the day (Wikimedia.org).

During the daytime hours, the planetary boundary layer comprises the surface layer, which is the lowest part. It features a super adiabatic lapse rate, moisture decrease with height. In windy conditions, the surface layer is characterized by a strong wind shear caused by friction. Above a surface layer, the mixed layer is located, where next to a horizontal air mass movement the vertical, turbulent updrafts play the main role. The air is risen up very quick (with up to 40km/h velocity). The convective mixed layer has a nearly constant distribution of the potential temperature, wind speed, humidity, and haze concentration, because of strong buoyancy generated convective turbulent mixing.  Once the supersaturation of the air is sufficient, then clouds start to form. It happens at the upper part of the planetary boundary layer, which forms the cloud cover or entrainment zone during the day. The condensation of moist air, containing aerosol releases energy, creates buoyancy and clouds rise until they reach their level of neutral buoyancy.
Rising air particles are replaced by drier air from the free atmosphere, that penetrates down the planetary boundary layer. Hence during the day, when some cumulus clouds start to appear in the sky, the visual range appears to be better, than in the morning. The air, that penetrates down from the free atmosphere, doesn’t contain as many aerosols as the rising air does.
Between the upper edge of the cloud layer, reliant of the highest thermal plume and the deepest part of the sinking free air is called the entrainment zone. This is the layer of intermittent turbulence and overshooting thermals at the top of the convective boundary layer. The thickness of the entrainment zone depends on the vibrancy of the turbulent movements. When turbulence and thermals are more vigorous, then the entrainment zone is thicker, unlike stronger temperature inversion caps, where is thinner. In this case, the cloud base will be a capping inversion layer during the day.  When Sun is going to set, then turbulence decays. As a result, the mixed layer is turned into a residual layer, which is neutrally stratified. Then turbulence is in near the same intensity in all directions. It means, that for instance, an emitted smoke plumes tend to disperse at equal rates in vertical and lateral directions, creating a cone-shaped plume (Stull, 1988). Above the residual layer, the capping inversion exists, on which level the cloud deck is produced, likewise in daytime conditions, when turbulence is weak. Sometimes the capping inversion can count about 40% of the whole planetary boundary layer. The capping inversion is an elevated inversion layer, that caps a convective boundary layer.  The capping inversion is caused by warmer air being above a region of cold air. Cloud formation from the lower layer is “capped” by the inversion layer. If the capping inversion is too strong, then it prevents a thunderstorm from developing, unless it is forced by strong updrafts. A strong cap can result in foggy conditions. The last issue, that I would like to add here is the general height of the planetary boundary layer. It is assumed, that a standard height is between 1,5 – 2 km above the ground. Practically the height of planetary boundary layer changes due to the weather conditions and may vary between 500 – 2500 m range.

Now let’s consider how it works with haze issues. The planetary boundary layer can be denoted by a thin layer of haze or a cloud deck that can be seen from the plane just after the start and before landing (Pic. 21, 22).  This layer or clouds deck can also be seen directly from the surface, especially when a lot of pollutants are trapped inside (Pic. 18) or after sunset, when it is not directly illuminated (Pic. 19).

Planetary boundary layer with trapped pollutants above Bieszczady

Pic. 18 A planetary boundary layer with a lot of trapped pollutants, seen from Wielka Rawka, 1307m.a.s.l (credits: Robert Bogacz).

Tatry, Łukasz Ruszała planetary boundary layer in the atmosphere after susnet

Pic. 19 Presence of the atmospheric boundary layer (shown red arrow) after sunset as seen from altitude a few hundred m.a.s.l. The Tatra Mts beyond having about 2,5 km.a.s.l, thus their peaks reach the “free atmosphere” with perfect visibility (credits: Łukasz Ruszała).

Capping inversion seen from Pico del Teide

Pic. 20 The capping inversion can be easily seen from freestanding mountains like the Pico del Teide is. Tenerife, Spain.

atmosphere boundary layer seen from the aircraft KRK-OSL

Pic. 21 The planetary boundary layer seen from the plane. The upper part of the layer during the daytime hours is marked by the cloud layer. When the cloud layer is nonuniform or patchy only, then a layer of trapped haze marks the planetary boundary layer. KRK – OSL.

Capping inversion seen from the plane RZE-STN

Pic. 22 An example of capping inversion as seen around 1,5-2 km above ground, RZE-STN.

Capping inversion Tatra Mts see a bit above from the aircraft RZE-STN

Pic. 23 An example of different levels of the planetary boundary layer, as seen in relation to high-mountains and much lower area. Red arrow indicates the High and Bielskie Tatras ridge rising above capping inversion (1,9 – 2 km.a.g.l). Mountains are still covered by layered clouds, however, the inversion pattern is different, RZE-STN.

To rundown this section I can say, that haze is always bigger within the planetary boundary layer because:

  • The air mass movement inside the planetary boundary layer is slower than in the above “free atmosphere” space so the ventilation of the area is also lower,
  • Planetary boundary layer gathers the water evaporated into the air from the biosphere, hence the humidity level is higher than in “free atmosphere”,
  • This is the part of the atmosphere, where the temperature inversion layer forms as a stable layer. Due to this a lot of air pollutants and aerosols concentrates there and deteriorates the visibility.
  • Other meteorological conditions like wind direction. Wind can transport the aerosols from different regions featured with another kind of surface, like e.g sand. Other unfavourable weather conditions can be stability stratification

The structure of the planetary boundary layer varies within the season, weather condition and time of the day. The depth of this layer is bigger during the night and winter and smaller in the summer and during daytime hours. The biggest haze will occur in the surface layer.

3. RELATION WITH INVERSION

The inversion phenomenon is very important in haze conditions because it traps air pollution, such a smog close to the ground. An inversion can also suppress convection by acting as a “cap”.

An issue with capped inversion has been explained in the section above. In this section, I would like to focus on the inversion layer, which is a subsidence and radiation inversion. There are two common types of temperature inversion, as occur mainly in the surface layer. As we know from the previous section, the inversion plays an important role in determining cloud forms, precipitation, and visibility. Both the capping inversion with the subsidence and radiation inversion affects diurnal variation in air temperature.  The principal heating of the air is caused by its contact with a land surface that has been heated by the Sun’s radiation. Then this warm air is transferred to the atmosphere by conduction and convection. Once evening approaches (roughly when Sun is about to set) this proportion changes. The air just above the ground, which was warmer during the day, now become colder, because ground cools off. Heat is radiating towards the sky, thus the radiation inversion is produced. The radiation inversion traps moisture and pollution. It results in a morning fog or thick smog, depending on when you live.

Radiation inversion above London seen from the plane LTN-WAW

Pic. 24 The radiation inversion enshrouding the Greater London, LTN-WAW.

When the widespread layer of air descends, what happens under a deep high-pressure area, the subsidence inversion develops. The layer is compressed and heated by the resulting increase of atmospheric pressure. If the air mass sinks low enough, the air at higher altitudes becomes warmer, than at lower altitudes; a temperature inversion is produced.
Subsidence inversions are common, especially during the winter. It can also occur on the lee side of a mountain range. This inversion also traps the haze and pollutants. Depends on the pressure and weather conditions inside the anticyclone the thickness of the subsidence inversion can vary up to several hundred meters.

Suchora, obserwatorium astronomiczne UP (10) Beskid Żywiecki, Syhlec 1145m, Babia Góra 1725m, Pilsko

Pic. 25 An example of the subsidence inversion in the mountainous area, where valleys and basins are covered by a thick layer of haze, trapped inside the inversion layer, whereas the air above is pristine. Suhora 1000 m.a.s.l, Gorce, Poland.

4. HAZE IMPACT ON VISIBILITY

Visibility can be defined as a degree of atmospheric clarity (Malm, 2016). Haze can be treated as a kind of bad weather, because it can significantly degrade the visibility of a scene. This phenomenon tends to produce a distinctive gray hue, which affects atmospheric transparency. Optically, this is due to the substantial presence of particles in the atmosphere, that absorb and scatter light (Tan, 2008). Light from the atmosphere and light reflected from an object are absorbed and scattered by these particles, causing the visibility of a scene to be degraded (Pic. 25 – 26).

Visibility impairment by haze

Pic. 26 The visibility impairment scheme, caused by dense haze or water droplets. Sunlight is scattered by aerosol particles (atmo.arizona.edu).

Haze visibility impairment caused by water droplets or haze

Pic. 27 The visibility impairment, caused by dense haze or water droplet (atmo.arizona.edu).

The visibility conditions differ mainly in the types and sizes of the particles involved in their concentration in space (Nayar,Narasimhan, 1999). The manner in which a particle scatters incident light depends on its material properties, shape and size  (Nayar, Narasimhan, 1999). The exact form and intensity of the scattering pattern vary dramatically with particle size (Minnaert, 1954). The extremely high concentration of these small particles can appreciably diminish the horizontal visibility. The transparency of the atmosphere increases when the aerosols are removed from the atmosphere. These particles can be removed by two mechanisms: deposition at Earth’s surface  (dry deposition) and incorporation into cloud or rain droplets during the formation of precipitation (wet deposition) (Pandis, Seinfeld, 2016).
The concentration of haze nucleic depends on wind and humidity. More information about this has been shown in the 1st section of this article. Wind disperses and transports the aerosols, whereas the humidity causes a hygroscopic growth of haze particles, especially high near-surface humidity. Another factor for the development of the haze is a dynamic mechanism. The boundary layer is controlled by the descending movement, which suppresses the vertical transportation of the aerosols. Tropospheric aerosols vary widely in concentration and composition over the Earth. This is caused by the nonuniformity of the geographic distribution of particles and kind of depositions being reliant on the local weather conditions.
In the result, the horizontal visibility in one area can differ from horizontal visibility in another (sometimes even adjacent) region. Haze impact on visibility is weather-dependant. Before the short term forecast has been developed people used to predict the weather by changes the visibility. For instance, before cold or warm front visibility is getting worse unlike after passing the cold front, when it is very good because the descent airflow facilitates to decreasing of aerosols particle concentrations (Marmureanu et all, 2017).
In European conditions, usually polar and arctic air mass brings the best horizontal visibility, unlike tropical masses with a high level of dust or moisture.
In meteorology, visibility is a measure of distance at which an object or light can be clearly discerned. In extremely clean air the visibility can be more than 320 km (200 miles) where there are large markers such as mountains or high ridges. The visual range is described in the 10-degree scale where 0 means thick fog with visibility lower than 50 m and 9 means extremely good visibility with a distance longer than 50 km.
The arctic (and antarctic) air mass is the clearest because it contains the lowest amount of particles coming from the local basement. Hence when is no products of water vapor condensation this air is almost perfect. The polar continental air mass and arctic maritime air mass is believed to have one of the highest transparency level due to lack of the anthropogenic factor and dust. Under haze-free atmospheric conditions, the light is scattered on air molecules only.  In this case, diffuse sky radiation restricts only to near-Rayleigh light scattering conditions, where short wavelengths are scattered more than longer ones during the day. It doesn’t mean, that under haze-free weather conditions our remote horizon will be clearly visible. Always, even on the clearest day, the remote horizon will have a blue appearance. There are basically two reasons for it:
– air-tiny hydrocarbon particles released by vegetation and next chemically react with ozone molecules, scattering a blue light selectively,
– air molecules, which scatters only short wavelengths according to Rayleigh scattering.

distant_blue_mountains light scattering on molecules

Pic. 28 A mechanism of light scattering on air molecules and its impact on the visual range (atmo.arizona.edu).

Horizon blue appearance Canyonlands National Park

Pic. 29 Even under haze-free conditions, an observer cannot see the remote horizon ideally, which has a bluish appearance. Canyonlands National Park, Utah.

Generally, the maritime air masses provide better visibility conditions than continental ones, because they are clear. However, these masses provide favorable moisture conditions for the occurrence of a haze event. The worst visibility is to observe during the tropical continental air mass advection, where a lot of dust raised by the wind from the ground. Much more details about the visual range changes will be provided in forthcoming articles soon.

5. WEATHER FORECAST

Most weather forecast services do not focus on the haze prediction itself.  It remains a second-order weather element. The best way is to check the relative humidity or visibility forecast. It should bring a piece of relevant information about the haze density. In terms of the visibility forecast helpful can be a dew point forecast. On the other hand, the air pollution forecast is widely accessible, which has been raised in the previous article.

Visibility meteo icm

Pic. 30 The visibility numerical forecast for Central Europe (meteo.icm.edu.pl).

Relative humidity map modellzentrale.de

Pic. 31 The relative humidity numerical forecast for Central Europe (modellzentrale.de).

Relative humidity map for USA

Pic. 32 The relative humidity forecast for USA & Canada (see legend in top right corner) along with the temperature and pressure (wxmaps.org).

Humidity real time for UK

Pic. 33 A real-time humidity forecast for the southern part of the UK (wunderground.com).

The aforementioned numerical weather patterns show only a general situation in a few countries at once, which can be helpful for plan long-distance observations. There is another way to check the visual range forecast. An example you can see in the picture below, but I will explain it in the forthcoming article about visibility.

Windy com dust mass Poland

Pic. 34 The windy.com weather forecast appears to be the best for checking the haze impact on the visual range. You can pick up a relevant layer such a “Dust mass”, “CO concentration”, “Visibility” or “Humidity” and asses the visual range conditions for a particular place (Windy.com).

6. CONCLUSIONS

Haze is an important weather factor, which can affect many issues from atmospheric light scattering even to impact human health  (air pollution). For the long-distance photography purposes haze results in the visual effect of a loss of contrast in the subject, due to the effect of light scattering through the haze particles. For these reasons, sunrise and sunset colors appear subdued on hazy days and stars may be obscured at night. In some cases, attenuation by haze is so great that, toward sunset, the sun disappears altogether before reaching the horizon. Big haze concentration deteriorates the human health causing the eyes, nose and lungs afflictions. Air pollution is also a hazard for expecting mothers. Big haze concentration modifies a light scattering in the lower part of the atmosphere making the sky brighter than it really is.  The biggest haze concentration is related to the planetary boundary layer (unified haze) within the inversion layer may exist (layered haze). This text provides general knowledge only. Is a lot of things to develop in the next articles.

Mariusz Krukar

 

References:

1. Ackerman S.A., Knox J. A., 2007, Meteorology: understanding the atmosphere, Thompson higher education, Belmont, CA.
3. Bohren C.F., Huffman D. R., 1983, Absorption and scattering of light by small particles, John Wiley & Sons, Weinheim
4. Hackel H., 2009, Pogoda i klimat, Multico, Warszawa
5. Hinds W. C., 1999, Aerosol technology: properties, behaviour and measurement of airborne particles, John Wiley, New York
6. Horvath H., 1993, Atmospheric light absorption – A review, (in:) Atmospheric environment. Part A. General topics, vol. 27, i.3 p. 293-317
7. Khalizov A.F., et. all, 2009, Enhanced light scattering by carbon soot aerosol internally mixed with sulfuric acid (in:) Journal Physic Chemistry, vol. 111, p. 1066 – 1074
8. Kokhanovsky A.A., 2008, Light absorption and scattering by particles in the atmosphere, Praxis Publishing, Chichester
9. Liou K., N., 2002, An introduction to atmospheric radiation, 2nd edition, Academic, San Diego.
10. Lundgren D.A., Cooper D.W., 1969, Effect of  humidity on light-scattering methods of measuring particle concentration, (in:) Journal of the Air Pollution Control Association, p.243-247
11. Malm W., 2016, Visibility: The seeing of near and distant landscape features, Elsevier Science
12. Marmureanu L, et al., 2017, Planetary boundary layer height influence on ground base aerosol concentrations, (in:) The European Aerosol COnference, Zurich 2017
13. Meland B.S., 2011, An investigation into particle shape effects on the light scattering properties of mineral dust aerosol, University of Iowa
14. Minnaert M., 1954, The nature of light and color in the open air, Dover, New York
15. Nayar K. S., Narasimhan G., S., 1999, Computer vision in bad weather (in:) Technical Report, Department of Computer Science, Columbia University, New York
16. Reid E.A., et. all., 2003, Characterization of African dust transported to Puerto Rico by individual particle and size segregated bulk analysis (in:) Journal Geophysics Researches
17. Stull R. B., 1988, An introduction to boundary layer meteorology, Kluwer Academic Publishers, Dordrecht
18. Tan R.T., 2008, Visibility in bad weather from a single image, Imperial College London

 

Links:

1. Scattering of light – graphs
2. Britannica.com: Planetary-boundary-layer
3. USA: The hazy days conditions. Comparison between non-haze and haze conditions
4. Metoffice.gov.uk: Types of humidity
5. Planetary boundary layer
6. Atmosphere boundary layer structure
7. Britannica: Temperature inversion
8. Radiation_inversions.htm
9. http://www.atmo.arizona.edu/students/courselinks/fall16/atmo170a1s3/1S1P_stuff/scattering_of_light/scattering_of_light.html

 

Wiki:

  1. Capping_inversion
  2. Convective_Boundary_Layer
  3. Distribution_of_particles
  4. Equilibrium_level
  5. Forward_scatter
  6. Inversion_(meteorology)
  7. Inversion_temperature
  8. Lapse_rate
  9. Particulates
  10. Planetary_boundary_layer
  11. Potential_temperature
  12. Surface_layer

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