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Volume 1 - The Atmospheric Studies Group at TRC

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Geophysical Processing<br />

Gridded land use and terrain elev<strong>at</strong>ion d<strong>at</strong>a for the CALMET geophysical file are<br />

obtained from the USGS. <strong>The</strong> terrain d<strong>at</strong>a are from the one-degree 1:250,000-scale<br />

DEM d<strong>at</strong>aset, with an approxim<strong>at</strong>e resolution of 90m. Land use d<strong>at</strong>a are from the<br />

1:250,000-scale Composite Grid <strong>The</strong>me (CTG) d<strong>at</strong>aset, with a resolution of 200m.<br />

Because the sp<strong>at</strong>ial vari<strong>at</strong>ion in land use is the primary geophysical property for this<br />

applic<strong>at</strong>ion, a modeling grid is chosen th<strong>at</strong> places each land use d<strong>at</strong>apoint in the<br />

center of a model grid cell. <strong>The</strong> modeling grid chosen to cover the area is defined by:<br />

Map Projection: UTM (Zone 11N)<br />

D<strong>at</strong>um: NAS-C (North American 1927)<br />

SW Corner Coordin<strong>at</strong>es (km): (282.1, 3779.1)<br />

Number of cells (nx,ny): (115,100)<br />

Cell Size (km): 0.200<br />

<strong>The</strong> CALMET preprocessors TERREL, CTGPROC, and MAKEGEO are applied to<br />

convert the geophysical d<strong>at</strong>asets to this modeling grid, cre<strong>at</strong>ing the CALMET<br />

GEO.DAT file.<br />

Coordin<strong>at</strong>e transform<strong>at</strong>ions are applied to the source and receptor loc<strong>at</strong>ions listed in<br />

the OCD4 model runs in order to register these fe<strong>at</strong>ures to land use and terrain d<strong>at</strong>a in<br />

the GEO.DAT file. <strong>The</strong> OCD4 d<strong>at</strong>aset uses a local grid system th<strong>at</strong> is not referenced<br />

to UTM coordin<strong>at</strong>es. <strong>The</strong>se (x,y) coordin<strong>at</strong>es are transl<strong>at</strong>ed to align the sampler<br />

loc<strong>at</strong>ions with roadway fe<strong>at</strong>ures th<strong>at</strong> are discernable on aerial photographs and th<strong>at</strong><br />

are indic<strong>at</strong>ed on the experiment site map.<br />

<strong>The</strong> resulting map of the experiment region is shown in Figure 4-4. Sampling Arc 1,<br />

nearest the coast, lies <strong>at</strong> elev<strong>at</strong>ions between 3m and 6m. Most of sampling Arc 2 lies<br />

<strong>at</strong> elev<strong>at</strong>ions between 15m and 25m, but the terrain <strong>at</strong> the northern end rises to more<br />

than 100m.<br />

Source & Receptor Characteriz<strong>at</strong>ion<br />

Tracer releases are characterized as modeled in the OCD4 evalu<strong>at</strong>ion. All are<br />

modeled with downwash, using the bo<strong>at</strong> dimensions as a solid building with the<br />

length perpendicular to the wind. A minimal exit velocity is used to remove any<br />

momentum rise.<br />

Final Report Vol.1 45

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