in the number of divisions reduces the overall coverage of the sampling domain when the

maximum number of grid points are specified. Since the size/resolution of the sampling

domain controls the amount of MESOPUFF II output produced, it should not be larger than

absolutely necessary.

In preparing the Phase 1 demonstration protocol, we recognized that the use of gridded

receptors greatly increases the amount of output produced by MESOPUFF II. In an effort to

control MESOPUFF II computation time and the size of sampling output we did not anticipate

using the sampling grid in the demonstration application of MESOPUFF II. Model

concentrations and fluxes were calculated at non-gridded receptor locations only.

Non-Gridded Receptor Locations

As discussed in the protocol, receptor sites were to be located within SNP and JRFW.

Receptor sites within SNP were to be distributed in a manner that represented the entire park,

but not so densely that nearly identical results would be obtained at neighboring receptors.

For a grid spacing of 20 km and sources located 50 to 200 km from the park, a spacing

between receptors of 5-10 km was expected to be adequate. Additionally, we had planned to

place several receptors outside SNP and JRFW, between the sources and the Class I area

receptors. These were to be selected after the locations of sources to be modeled had been

provided. Decisions on receptor selection for future MESOPUFF II applications should be

made on a case-by-case basis.

Selection of Non-Gridded Receptors

We received UTM coordinates for 200 receptor locations in SNP and 67 receptor locations in

JRFW from VDEQ (Browder, 1993). The specification of 267 non-gridded receptors within

MESOPUFF II would have resulted in larger amounts of output than would have been optimal

for post-processing. Furthermore, many of the receptors were located very close together, and

the model was not expected to be able to resolve the differences between them. Therefore, we

selected a subset of the receptors to be used in the MESOPUFF II demonstration modeling.

A simple approach was developed to estimate the minimum spacing for which concentration

differences would be modeled. Since the sources were to be at least 50 km from the receptors,

we examined downwind plume widths at 50 km using the Pasquill-Gifford-Turner dispersion

curves. The plume width at 50 km for D stability is approximately 8 to 9 km. Half the

expected plume width, or roughly 4 to 5 km, was used as a guideline in selecting non-gridded

receptors for MESOPUFF II.

Figure 3-2(a) displays the entire MESOPUFF II computational domain, where the insets

denote the placement and extent of the SNP and JRFW receptor areas shown in Figures 3-2(b)

and 3-2(c), respectively. Figure 3-2(b) presents the array of receptors for SNP, and identifies

those selected as MESOPUFF II receptors (denoted as circles). Receptors

 

 

n1301 - n1302 - n1303 - n1304 - n1305 - n1306 - n1307 - n1308 - n1309 - n1310 - n1311 - n1312 - n1313 - n1314 - n1315 - n1316 - n1317 - n1318 - n1319 - n1320 - n1321 - n1322 - n1323 - n1324 - n1325 - n1326 - n1327 - n1328 - n1329 - n1330 - n1331 - n1332 - n1333 - n1334 - n1335 - n1336 - n1337 - n1338 - n1339 - n1340 - n1341 - n1342 - n1343 - n1344 - n1345 - n1346 - n13247 - n1348 - n1349 - n1350

 

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