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Table 6‐1. Summary <strong>of</strong> model ranking using <strong>the</strong> statistical performance metrics.<br />

Statistic 1 st 2 nd<br />

3 rd<br />

4 th 5 th<br />

FMS CAMx SCIPUFF HYSPLIT FLEXPART <strong>CALPUFF</strong><br />

FAR HYSPLIT FLEXPART CAMx SCIPUFF <strong>CALPUFF</strong><br />

POD CAMx SCIPUFF HYSPLIT FLEXPART <strong>CALPUFF</strong><br />

TS CAMx HYSPLIT SCIPUFF FLEXPART <strong>CALPUFF</strong><br />

FOEX CAMx SCIPUFF HYSPLIT FLEXPART <strong>CALPUFF</strong><br />

FA2 CAMx SCIPUFF HYSPLIT FLEXPART <strong>CALPUFF</strong><br />

FA5 CAMx SCIPUFF HYSPLIT FLEXPART <strong>CALPUFF</strong><br />

NMSE HYSPLIT CAMx <strong>CALPUFF</strong> FLEXPART SCIPUFF<br />

PCC or R SCIPUFF HYSPLIT CAMx FLEXPART <strong>CALPUFF</strong><br />

FB HYSPLIT CAMx <strong>CALPUFF</strong> FLEXPART SCIPUFF<br />

KS CAMx SCIPUFF HYSPLIT FLEXPART <strong>CALPUFF</strong><br />

Avg. Ranking CAMx HYSPLIT SCIPUFF FLEXPART <strong>CALPUFF</strong><br />

Avg. Score 1.55 2.27 2.73 3.82 4.64<br />

RANK Ranking CAMx HYSPLIT SCIPUFF FLEXPART <strong>CALPUFF</strong><br />

6.4.2 Spatial Displays <strong>of</strong> Model Performance<br />

Figure 6‐16 displays <strong>the</strong> observed tracer distribution 24, 36, 48 <strong>and</strong> 60 hours after <strong>the</strong> beginning<br />

<strong>of</strong> <strong>the</strong> tracer release as well as <strong>the</strong> predicted tracer distribution by <strong>CALPUFF</strong>, SCIPUFF, FLEXPART<br />

<strong>and</strong> CAMx. Note that <strong>the</strong> observed tracer spatial distribution plots in Figure 6‐16 are color<br />

coded at <strong>the</strong> monitoring sites. Previously <strong>the</strong> spatial distribution <strong>of</strong> <strong>the</strong> observed tracer<br />

distribution was also presented using spatial interpolation from <strong>the</strong> monitoring sites in Figure 6‐<br />

3b. However, such an interpolation is in itself a model <strong>and</strong> may not be correct, so in Figure 6‐16<br />

<strong>the</strong> observed tracer concentrations at <strong>the</strong> monitoring sites is presented for comparison with<br />

<strong>the</strong> five LRT models.<br />

24 hours after <strong>the</strong> tracer release, <strong>the</strong> observed tracer was advected to <strong>the</strong> east‐nor<strong>the</strong>ast <strong>and</strong><br />

was present across nor<strong>the</strong>rn France <strong>and</strong> Germany (Figure 6‐16a, top left). <strong>CALPUFF</strong> advected<br />

<strong>the</strong> tracer with a more nor<strong>the</strong>asterly direction than observed <strong>and</strong> underestimated <strong>the</strong> plume<br />

spread <strong>the</strong>reby missing <strong>the</strong> observed tracer concentrations in sou<strong>the</strong>rn Germany (Figure 6‐16a,<br />

top right). SCIPUFF (Figure 6‐16a, middle left) also appeared to advect <strong>the</strong> tracer with more <strong>of</strong><br />

a nor<strong>the</strong>ast direction than observed, but had more plume spread so was better able to capture<br />

<strong>the</strong> occurrence <strong>of</strong> observed tracer concentrations in sou<strong>the</strong>rn Germany. FLEXPART (Figure 6‐<br />

16a, middle right) <strong>and</strong> HYSPLIT (Figure 6‐16a, bottom left) both correctly advect <strong>the</strong> tracer<br />

initially in <strong>the</strong> east‐nor<strong>the</strong>ast direction, but FLEXPART greatly underestimates <strong>the</strong> observed<br />

plume spread on <strong>the</strong> ground with HYSPLIT also underestimating <strong>the</strong> plume spread but not as<br />

much as FLEXPART. CAMx also appears to initially transport <strong>the</strong> tracer with more <strong>of</strong> a<br />

nor<strong>the</strong>asterly than east‐nor<strong>the</strong>ast direction as seen with SCIPUFF. Like SCIPUFF, <strong>the</strong> CAMx<br />

tracer plume has a sou<strong>the</strong>rly bulge that begins to capture <strong>the</strong> occurrence <strong>of</strong> <strong>the</strong> observed tracer<br />

concentrations in sou<strong>the</strong>rn Germany that <strong>the</strong> o<strong>the</strong>r three LRT dispersion models miss<br />

completely. All <strong>of</strong> <strong>the</strong> models fail to reproduce <strong>the</strong> leading edge <strong>of</strong> <strong>the</strong> observed tracer cloud in<br />

nor<strong>the</strong>astern Germany, with SCIPUFF <strong>and</strong> CAMx best able to simulate <strong>the</strong> observed front <strong>of</strong> <strong>the</strong><br />

tracer cloud. The LRT dispersion models underestimation <strong>of</strong> <strong>the</strong> location <strong>of</strong> <strong>the</strong> leading edge <strong>of</strong><br />

<strong>the</strong> observed tracer cloud is likely related to <strong>the</strong> MM5 model wind speed underestimation bias<br />

(see Figure 6‐4a). SCIPUFF tends to have an overestimation bias <strong>of</strong> both concentrations <strong>and</strong><br />

spatial extend <strong>of</strong> <strong>the</strong> observed tracer 24 hours after its release.<br />

The predicted <strong>and</strong> observed tracer distribution 36 hours after its release is shown in Figure 6‐<br />

16b. The observed tracer plume moved eastward <strong>and</strong> traverses Germany 36 hours after <strong>the</strong><br />

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