Volume 1 - The Atmospheric Studies Group at TRC

Geophysical Processing
Gridded land use and terrain elevation data for the CALMET geophysical file are
obtained from the U.S. Geological Survey. The terrain data are from the global 30
arc-second dataset GTOPO30, with an approximate resolution of 900m. Land use
data are from the global Lambert Azimuthal dataset, with a resolution of 1 km.
Because the data resolution is about 1 km, a modeling grid is chosen with the same
resolution, and uses the same projection and datum as positional data contained in the
dataset. The modeling grid chosen to cover the area is defined by:
Map Projection: UTM (Zone 33N)
Datum: EUR-M (European 1950)
SW Corner Coordinates (km): (300.0, 6130.0)
Number of cells (nx,ny): (100,100)
Cell Size (km): 1.000
The CALMET preprocessors TERREL, CTGPROC, and MAKEGEO are applied to
convert the geophysical datasets to this modeling grid, creating the CALMET
GEO.DAT file.
The resulting map of the experiment region is shown in Figure 4-5. The three
releases from the Gladsaxe tower are transported across about 7 km of urban/built-up
land in and around Copenhagen before reaching the strait. The six releases from the
Barseback tower are very near the strait, with a more rural upwind fetch.
Source & Receptor Characterization
Tracer releases are characterized as point sources and a minimal exit velocity is used
to remove any momentum rise. There is no downwash. Actual emission rates of the
tracer are modeled explicitly, although these rates are steady throughout an
experiment and vary little between experiments. All six of the releases from
Barseback are at 6.17 g/s, and those three from Gladsaxe are at 5.05 g/s, 5.09 g/s, and
5.39 g/s. Release times are typically on the hour or half hour, and last three to five
hours. These times are simulated in CALPUFF by using the diurnal emissions cycle
for point sources. The 24 emission factors in the cycle are set to 1.0 only during the
release period, and the release period begins at the start of the first hour of actual
release. If the tracer starts at 0830 CET (Central European Time), Hour 9 in the
diurnal array has the first non-zero value. These times and other point source
characteristics used in the modeling are listed in Table 4-9.
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