Similar results for the 6-week wintertime period are shown

in Figure 8 and Table 6. More observations are included in

this analysis because of the longer simulation period, and

also the STN network became operational in the urban areas.

The scatterplot shows that the urban STN data are generally

higher than the rural IMPROVE data, and that some of the

western sites have considerably higher aerosol

concentrations than eastern sites (mostly because of high

aerosol nitrate). The CMAQ model results generally were

within a factor of two of observations with reasonable

correlation (r=0.68) for the IMPROVE sites, but degraded

correlation (r=0.37) for the STN sites. Mean biases were

1.49 :g m-3 (40.3% as normalized bias) for the IMPROVE

stations, and 0.51 :g m-3 (4.1% as normalized bias) for the

STN stations. The model has a tendency to overpredict

concentrations in the winter application, although with

differing results among the aerosol components. Nitrate

aerosols were generally overpredicted, while organic

aerosols were underpredicted. Some of the STN stations in

the western U.S. showed much higher nitrate and organic

aerosol concentrations than the CMAQ model predicted.

This application illustrates that the CMAQ model is able to

simulate ozone and PM2.5 concentrations reasonably well

over the CONUS. There are many challenges, especially in

the area of aerosol modeling and interpreting the

observational data for model evaluation. We have seen that

different networks (urban vs. rural; east vs. west) can show

quite different characteristics in the ambient aerosols. In the

coming year, the CMAQ model will be used to simulate

ozone and PM2.5 for the full year of 2001 over the CONUS

for a more extensive model evaluation application.

10.2 Application to Houston-Galveston airshed high ozone




n1051 - n1052 - n1053 - n1054 - n1055 - n1056 - n1057 - n1058 - n1059 - n1060 - n1061 - n1062 - n1063 - n1064 - n1065 - n1066 - n1067 - n1068 - n1069 - n1070 - n1071 - n1072 - n1073 - n1074 - n1075 - n1076 - n1077 - n1078 - n1079 - n1080 - n1081 - n1082 - n1083 - n1084 - n1085 - n1086 - n1087 - n1088 - n1089 - n1090 - n1091 - n1092 - n1093 - n1094 - n1095 - n1096 - n1097 - n1098 - n1099 - n1100


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