Ecoinformatics Problems of Global Climate Change - New Ecoinformatics Tools in Environmental Science: Applications and Decision-making - page 468

In modeling, the scattering of gases and particles in the atmosphere is important to
know the difference between the polluted and clear atmosphere properties. Also, one
should always bear in mind the vertical heterogeneity of the atmosphere. On a global
scale, the formation of air quality depends on processes at all levels of the atmosphere:
the troposphere, stratosphere, hemosphere, and ionosphere. For instance, in the
problem of the impact of aviation on the atmosphere, it is necessary to take into
account the interaction between the troposphere and stratosphere. In studying the
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fluxes of pollutants from the surface sources, the motion of the lower atmosphere is
considered first of all. Of course, here of importance is the spatial scale and, hence, the

time interval of the pollutants residence in the atmosphere. Data known for the clear

atmosphere should be used in the control simulation experiments.
Pollutants emitted to the atmosphere are subject to gravitational sedimentation,
turbulent mixing, wind-driven transport, and washing out by rain. A totality of these
impacts determines the character of behavior of the polluting cloud, shape and type
of the

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flux of pollutants, as well as the spatial structure of the distribution of aerosol
number density over a given territory.
Smoke and other atmospheric aerosols are gravitationally in

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uenced and interact
with solar radiation, gases and ions. In the surface layer, this interaction is sup-
plemented with different effects of the surface (vegetation cover, soil, land surface
roughness, and sea surface roughness).
The role of sedimentation is more substantial in case of large particles, larger in
diameter than sub-micron particles. Small particles sediment are much slower
compared to their transport by the moving atmosphere, and therefore in many models
this vertical constituent is neglected. Note that for the process of sedimentation the
diameter of particles is less important than their density. For instance, soot structures
with a low ef

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cient density and large aerodynamic cross-section are easily wind-
driven and sediment much slower than the compact particles of the same mass. The
rate of sedimentation of particles with D = 0.1

m averages 0.001 m s − 1 , which is
negligibly small compared to the rate of atmospheric transport.
In case of heavily polluted formations one can observe the process of photo-
phores consisting in particles

1 ʼ

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lifting due to non-uniform solar heating. However,
the possibility of this phenomenon and its characteristics have been poorly studied,
therefore in a

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first approximation, many experts leave it out of account, especially
because during time intervals longer than a day, due to Brownian motion, an
irregular heating of particles decreases. Finally, such physical process should be
pointed out as particles coagulation consisting in capture of one particle by another
due to different rates of motion. In this case, particles can either stick together or be
repelled, so that diverse situations of their interactions arise which determine the
shape of the cloud of pollutants and can prolong their lifetime in the atmosphere.
The washing-out is a very important process of removal of pollutants from the
atmosphere. Here two situations are possible. One is connected with a simple
capture of particles by rain droplets,

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with the so-called nucleation
process. This process is connected with oversaturated water vapor condensation on

the other