Analytical Models for the Dispersion of Pollutants in Low Wind Conditions 175
from each other on various counts such as on the height of the release (near- surface,
elevated), underlying terrain, and the atmospheric stability. The comprehensive
reviews on some of these experiments are given in the literature (Pasquill and Smith,
1983; Draxler, 1984; Arya, 1999). Sharan et al. (2003) have briefl y described the
salient features of some of these diffusion experiments. It is necessary to plan the
extensive fi eld program involving both tracer and meteorological measurements in
low wind conditions for evaluation and updating these models.
We have discussed the analytical models for the dispersion of pollutants in low
wind conditions. In addition, numerical models and Lagrangian particle models
have been used in the literature for simulation in the low wind conditions (Anfossi
et al., 1990; Brusasca et al., 1992; Arya, 1999; Oettl et al., 2001; Sharan and
Gopalakrishnan, 2003). Since the aim of the study is to deal with the analytical
models; we have restricted our discussion in reference to the analytical studies for
the near source or low wind dispersion.
6.5 SUMMARY
In view of the limitations of the applicability of dispersion models in low wind
conditions, an attempt has been made to provide an overview on analytical models
for dispersion of air pollutants in these conditions. In the treatment of dispersion in
low wind conditions, limitations are associated with (1) parameterization of eddy
diffusivities, (2) parameterization of dispersion parameters, (3) incorporation of a
realistic wind profi le, and (4) availability of tracer and turbulent observations. The
commonly used parameterization schemes for sigma are lacking for estimation of
dispersion parameters in low wind conditions because (1) the state of the weak wind
ABL is not well defi ned, (2) plume spread in the horizontal direction is increased
because of meandering, and (3) nonavailability of adequate observations. There is
a need for an extensive fi eld program comprising (1) diffusion measurements and
(2) meteorological measurements including surface/upper air and turbulence observations. A general parameterization of eddy diffusivities for the treatment of nearsource dispersion is desired for the formulation of a more realistic dispersion model
valid for all wind speeds. Since the aim of the study is to deal with the analytical
models, we have restricted our discussion in reference to the analytical studies for the
near source or low wind dispersion.
REFERENCES
Adachi, T. and Ohta, S.: (1978), Atmospheric diffusion under very low wind speed, very stable
conditions, Fourth US/JAPAN Joint Meeting on Air Pollution Related Meteorology,
December 11–15, U.S. Environmental Protection Agency, Washington, DC.
Anfossi, D., Brusasca, G., and Tinarelli, G.: (1990), Simulation of atmospheric diffusion in
low wind speed meandering conditions by a Monte-Carlo dispersion model, II Nuovo
Cimento 13, 277–282.
Arya, S. P.: (1995) Modeling and parameterization of near-source diffusion in weak winds,
J. Appl. Meteorol. 34, 1112–1122.
Arya, S. P.: (1999), Air Pollution Meteorology and Dispersion, Oxford University Press,
New York. 320 pp.
© 2010 by Taylor and Francis Group, LLC
from each other on various counts such as on the height of the release (near- surface,
elevated), underlying terrain, and the atmospheric stability. The comprehensive
reviews on some of these experiments are given in the literature (Pasquill and Smith,
1983; Draxler, 1984; Arya, 1999). Sharan et al. (2003) have briefl y described the
salient features of some of these diffusion experiments. It is necessary to plan the
extensive fi eld program involving both tracer and meteorological measurements in
low wind conditions for evaluation and updating these models.
We have discussed the analytical models for the dispersion of pollutants in low
wind conditions. In addition, numerical models and Lagrangian particle models
have been used in the literature for simulation in the low wind conditions (Anfossi
et al., 1990; Brusasca et al., 1992; Arya, 1999; Oettl et al., 2001; Sharan and
Gopalakrishnan, 2003). Since the aim of the study is to deal with the analytical
models; we have restricted our discussion in reference to the analytical studies for
the near source or low wind dispersion.
6.5 SUMMARY
In view of the limitations of the applicability of dispersion models in low wind
conditions, an attempt has been made to provide an overview on analytical models
for dispersion of air pollutants in these conditions. In the treatment of dispersion in
low wind conditions, limitations are associated with (1) parameterization of eddy
diffusivities, (2) parameterization of dispersion parameters, (3) incorporation of a
realistic wind profi le, and (4) availability of tracer and turbulent observations. The
commonly used parameterization schemes for sigma are lacking for estimation of
dispersion parameters in low wind conditions because (1) the state of the weak wind
ABL is not well defi ned, (2) plume spread in the horizontal direction is increased
because of meandering, and (3) nonavailability of adequate observations. There is
a need for an extensive fi eld program comprising (1) diffusion measurements and
(2) meteorological measurements including surface/upper air and turbulence observations. A general parameterization of eddy diffusivities for the treatment of nearsource dispersion is desired for the formulation of a more realistic dispersion model
valid for all wind speeds. Since the aim of the study is to deal with the analytical
models, we have restricted our discussion in reference to the analytical studies for the
near source or low wind dispersion.
REFERENCES
Adachi, T. and Ohta, S.: (1978), Atmospheric diffusion under very low wind speed, very stable
conditions, Fourth US/JAPAN Joint Meeting on Air Pollution Related Meteorology,
December 11–15, U.S. Environmental Protection Agency, Washington, DC.
Anfossi, D., Brusasca, G., and Tinarelli, G.: (1990), Simulation of atmospheric diffusion in
low wind speed meandering conditions by a Monte-Carlo dispersion model, II Nuovo
Cimento 13, 277–282.
Arya, S. P.: (1995) Modeling and parameterization of near-source diffusion in weak winds,
J. Appl. Meteorol. 34, 1112–1122.
Arya, S. P.: (1999), Air Pollution Meteorology and Dispersion, Oxford University Press,
New York. 320 pp.
© 2010 by Taylor and Francis Group, LLC