temporally varying wind field from that hour and previous

hours. Therefore, the exact behavior of a given modeling

system relative to a similar but different modeling system can

not be predicted with certainty.

 

2. EXISTING MODEL COMPARISONS AND

EVALUATIONS

There have been a number of surveys of long range

transport models which may be suitable for estimating the

concentrations of pollutants which degrade visibility and/or

contribute to acid deposition. One such survey (Thompson et

al., 1987) used a series of screenings and rankings to narrow

the field of Lagrangian, Eulerian, hybrid, and statistical

models which they would consider for application in western

Canada. The model characteristics this study considered

important were:

a. domain - 0 to 500 km and up to one year

b. resolution - 1 to 10 km and event to seasonal

c. predictands - ambient air concentrations of SO , SO , 2 4

=

HF, metals, oxidants and NOX

d. processes - convective and frontal storms, flow in

complex terrain, rain and snow scavenging, influences

of soil particles, cloud physics and chemistry

e. design - modular

f. accuracy - ±30 percent for sulfate concentration and

deposition

g. chemistry - nonlinear.

The desire for a model which exhibits these characteristics is

also shared by the IWAQM. A relatively small number of the

potentially available models were identified through this

process. The MESOPUFF-II model was among the models identified

as meeting the criteria of the survey.

Another review of models was conducted for the EPA as part

of the Rocky Mountain Acid Deposition Model Assessment (Morris

and Kessler, 1987). The conclusion of this study was that

"...no one meteorological or acid deposition model is

significantly superior to the others; all the candidate models

 

n1251 - n1252 - n1253 - n1254 - n1255 - n1256 - n1257 - n1258 - n1259 - n1260 - n1261 - n1262 - n1263 - n1264 - n1265 - n1266 - n1267 - n1268 - n1269 - n1270 - n1271 - n1272 - n1273 - n1274 - n1275 - n1276 - n1277 - n1278 - n1279 - n1280 - n1281 - n1282 - n1283 - n1284 - n1285 - n1286 - n1287 - n1288 - n1289 - n1290 - n1291 - n1292 - n1293 - n1294 - n1295 - n1296 - n1297 - n1298 - n1299 - n1300

 

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