air quality assessment & management
Reference and User Manual
Computational kernelThe high-resolution near field dispersion model for line sources (traffic) used is based on AERMOD, and uses a computational kernel based on an area source (Gaussian solution with an hourly aggregation period) with a mixing zone approach in and over the street itself with unit emissions. The mixing zone approach represents the high turbulence over and near the street itself, due to
The kernel results are then scaled according to actual traffic frequency, speed, and fleet composition, and distributed along the line sources by a convolution method.
The kernel is defined in terms of its resolution (default: 10m)
and size (1-5 km), and the mixing zone parameters,
expressed as a set of symbolic choices of algorithms.
In the latter case, the 24 kernel solution are using the actual hourly meteorological data, and the results can be viewed under an animation tape deck control.
To represent the turbulent mixing close to the source (street) due to the movement of vehicles, the kernel can be "tuned" with the application of a low-pass filter; the user defines the size of the "mixing zone" as well as the number of passes used to redistribute concentration (mass conservative) in the mixing zone.
The compairson of original and modified kernal shows the reduction of the original concentration maxima close to the source in the "middle of the street".
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