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Documentation of the Evaluation of CALPUFF and Other Long ...

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The RANK statistical performance metric was proposed by Draxler (2001) as a single model<br />

performance metric that equally ranks <strong>the</strong> combination <strong>of</strong> performance metrics for correlation<br />

(PCC or R), bias (FB), spatial analysis (FMS) <strong>and</strong> unpaired distribution comparisons (KS). The<br />

RANK metrics ranges from 0.0 to 4.0 with a perfect model receiving a score <strong>of</strong> 4.0. Figure 6‐15<br />

lists <strong>the</strong> RANK model performance statistics for <strong>the</strong> five LRT models. CAMx is <strong>the</strong> highest<br />

ranked model using <strong>the</strong> RANK metric with a value <strong>of</strong> 1.9. Note that CAMx scores high in all four<br />

areas <strong>of</strong> model performance (correlation, bias, spatial <strong>and</strong> cumulative distribution). The next<br />

highest ranking models according to <strong>the</strong> RANK metric are SCIPUFF <strong>and</strong> HYSPLIT with a score <strong>of</strong><br />

1.8.<br />

2.4<br />

2.0<br />

1.6<br />

1.2<br />

0.8<br />

0.4<br />

0.0<br />

<strong>CALPUFF</strong><br />

SCIPUFF<br />

Rank (RANK) (Perfect = 4)<br />

HYSPLIT<br />

Figure 6‐15. RANK statistical performance metric for <strong>the</strong> five LRT models <strong>and</strong> <strong>the</strong> ETEX tracer<br />

field experiment.<br />

6.4.1.3 Summary <strong>of</strong> Model Ranking using Statistical Performance Measures<br />

Table 6‐1 summarizes <strong>the</strong> rankings between <strong>the</strong> five LRT models for <strong>the</strong> 11 performance<br />

statistics analyzed. Depending on <strong>the</strong> statistical metric, three different models were ranked<br />

first for a particular statistic with CAMx being ranked first most <strong>of</strong> <strong>the</strong> time (64%) <strong>and</strong> HYSPLIT<br />

ranked first second most (27%). In order to come up with an overall rank across all eleven<br />

statistics we average <strong>the</strong> modeled ranking order in order to come up with an average ranking<br />

that listed CAMx first, HYSPLIT second, SCIPUFF third, FLEXPART fourth <strong>and</strong> <strong>CALPUFF</strong> <strong>the</strong> fifth.<br />

This is <strong>the</strong> same ranking as produced by <strong>the</strong> RANK integrated statistics that combines <strong>the</strong> four<br />

statistics for correlation (PCC), bias (FB), spatial (FMS) <strong>and</strong> cumulative distribution (KS) giving<br />

credence that <strong>the</strong> RANK statistic is a potentially useful performance statistic for indicating over<br />

all model performance <strong>of</strong> a LRT dispersion model.<br />

117<br />

FLEXPART<br />

CAMx<br />

(1‐KS/100)<br />

FMS/100<br />

(1‐FB/2)<br />

R^2

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