AirWare Reference Manual: line source model

AirWare On-line Reference Manual

Release Level	5.3.0 beta
Release Date	2007 06
Revision Level	1.1

Line source model

AirWare includes a very high resolution model (spatial resolutions from 5 to 50 meters) to describe near-field concentration gradients (from 500 m to 5 km around the source) for hourly events along roads and traffic arties.

The dispersion model used is based on AERMOD, and uses a computational kernel based on an area source (Gaussian solution with an hourly aggregation period in AERMOD) with a mixing zone approach in and over the street itself with unit emissions. 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.

Model Scenarios

The convolution based traffic model is available for

individual model domains and 24 hour runs of traffic sources only;
individual model domains and annual runs (on an hourly basis) for average and maximum concentrations;
individual road sources for 24 hours or on an annual basis;
as an integrated component in any AERMOD scenario, where point and area sources are cacluated by AERMOD, the line sources by the convolution method, and the results then combined and superimposed.

I all cases, the results of the basic kernel computations can be inspected, and several kernel parameters (resolution, size, mixing zone algorithm parametrisation) can be selected by the user.

Domain specific runs

For these scenarios, all line segments within the model domain will be used.

Road segment specific runs

The basic model is also linked to the line sources emission inventory for the analysis of individual line sources, one at a time..

The select primarily a road segment from the line source emission data base.

At the level of the line source model (button: Traffic model), available choices include:

Data (YYYY-MM-DD)
time (24 hour clock)
pollutant, selection from a pull-down menu
meteo scenario (defined by the station chosen)

Running the model for a single line sources takes only a few seconds, so it is done in the foreground while the user waits. Results are shown on the main page as a color coded overlay, transparent, over the map.

The button: details right under the map then leads to a larger map with interactive control of the results display, choice of color/histogram classification, display of sources, and zooming.

AERMOD with embedded convolution

AERMOD models runs also use the high-resolution convolution model for traffic sources;

AERMOD is run with emission from all point and area sources;
the convolution models is run, for the same meteorology, for the corresponding line sources, but with its full, 10 m resolution.
the two model result matrices are added together, aggregating the high-resolution convolution model results to the coarser resolution of the overall AERMOD scenario.