(BRAVO) Study: Final Report. - Desert Research Institute

Final Report — September 2004
Table 9-20. CMAQ-MADRID performance for sulfur species at the K-Bar site, BBNP, over the
duration of the BRAVO study.
Statistic Units 24-hr SO2
Weekly
SO2
24-hr
SO4 2–
24-hr Total
S
Weekly
Total S
Observed mean µg/m 3 0.88 0.87 2.49 1.25 1.30
Predicted mean µg/m 3 0.85 0.87 2.61 1.33 1.41
Coeff. of determination (r 2 ) 0.03 0.29 0.52 0.30 0.38
Mean bias µg/m 3 -0.04 -0.01 0.12 0.08 0.11
Mean error µg/m 3 0.72 0.33 1.08 0.64 0.39
Mean Normalized Bias % 85 16 20 34 9
Mean Normalized Error % 134 42 55 64 28
Fractional Bias % 0 5 0 8 4
Fractional Error % 72 38 46 48 27
RMS error µg/m 3 1.24 0.46 1.51 0.95 0.50
Table 9-21. CMAQ-MADRID performance for sulfur species at the Big Thicket site over the duration
of the BRAVO study.
Statistic
Units
24-hr
SO2
Weekly
SO2
24-hr
SO4 2–
24-hr
Total S
Weekly
Total S
Observed mean µg/m 3 1.03 1.04 4.18 1.91 1.94
Predicted mean µg/m 3 2.56 2.62 6.44 3.40 3.48
Coeff. of determination (r 2 ) 0.28 0.65 0.63 0.43 0.16
Mean bias µg/m 3 1.53 1.58 2.26 1.48 1.54
Mean error µg/m 3 1.73 1.63 2.67 1.60 1.54
Mean Normalized Bias % 239 149 57 95 81
Mean Normalized Error % 255 154 70 101 81
Fractional Bias % 63 73 32 50 53
Fractional Error % 88 79 47 58 53
RMS error µg/m 3 2.66 2.12 3.66 2.23 1.86
As illustrated by the time series in the top graph in Figure 9-26, the model is unable to
capture the evolution of SO 2 concentrations at Big Bend, as reflected by the low coefficient
of determination (r 2 = 0.03) given in Table 9-20. The model fails to capture the two principal
peak SO 2 events and predicts only one of the three lesser peak SO 2 events. The model also
predicts five sharp SO 2 peaks that were not observed in the field. Over all, the model
generally understated high concentration events and overstated periods of typically low
concentrations.
9-57