Environmental Engineering Reference
In-Depth Information
Utilization of Meandering in a Receptor-
Oriented Solution of the Line Source
Dispersion Equation
Jari Härkönen, Janne Berger, Mari Kauhaniemi, Juha Nikmo,
and Ari Karppinen
Introduction
Lateral long period fluctuation (meandering) of wind direction affects significantly
on the results of dispersion models
[1]
. Anfossi et al. showed that meandering exists
under all meteorological conditions
[2]
. Meandering seems to be independent on
stability conditions, but is especially important in low wind speed conditions.
Line source dispersion modeling results are particularly sensitive to meandering
because of the geometry of receptor - finite line source system. One may imagine
that lateral fluctuation of wind direction during the averaging time changes effec-
tively the real distance between the receptor point and line source as illustrated in
Fig.
1
. This influences substantially on the computed concentration at the receptor
point, because the concentration is a strongly nonlinear function of the distance
between point source S(x,0) and receptor R(x,y).
The aim of this work is to develop and test a specific meandering function
applicable to analytical line source dispersion models in local scale when nearly
parallel flows to the road are problematic.
Experimental Method
The measured NO
x
data includes 1,038 cases from 1 January to 15 April 2002 near
Oslo. The monitoring site with three monitors and the background monitor (B) is
shown in Fig.
2
.
J. Härkönen, M. Kauhaniemi, J. Nikmo and A. Karppinen
Finnish Meteorological Institute, Air Quality Research, Erik Palmenin Aukio 1, P.O. Box 503,
FI-00101 Helsinki, Finland
J. Berger
Norwegian Institute for Air Research (NILU), P.O. Box 100, NO, 2027, Kjeller, Norway
