Volume 1 - The Atmospheric Studies Group at TRC
Volume 1 - The Atmospheric Studies Group at TRC
Volume 1 - The Atmospheric Studies Group at TRC
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Oresund<br />
A total of 16 CALPUFF simul<strong>at</strong>ions are run for each experiment-hour in the Oresund<br />
d<strong>at</strong>aset to explore the sensitivity of model performance to the 4 CALMET<br />
configur<strong>at</strong>ions associ<strong>at</strong>ed with mixing height comput<strong>at</strong>ions and the 2 CALPUFF<br />
configur<strong>at</strong>ions associ<strong>at</strong>ed with the choice for minimum σ v . Predicted and observed<br />
concentr<strong>at</strong>ions for all of these simul<strong>at</strong>ions are listed in Tables 4-17 and 4-18.<br />
Analysis of these results leads to the following conclusions:<br />
• <strong>The</strong> choice for the convective mixing height model can change individual<br />
arc-peak concentr<strong>at</strong>ions in the Oresund d<strong>at</strong>aset by about 20%. On average,<br />
the B<strong>at</strong>chvarova–Gryning option (IMIXH=2) reduces these peak<br />
concentr<strong>at</strong>ions by about 10% from those obtained with the Maul-Carson<br />
option (IMIXH=1).<br />
• <strong>The</strong> choice of either calcul<strong>at</strong>ed overw<strong>at</strong>er mixing height or using the heights<br />
estim<strong>at</strong>ed from the temper<strong>at</strong>ure profiles over the strait (listed in Table 4-10)<br />
can change individual arc-peak concentr<strong>at</strong>ions in the Oresund d<strong>at</strong>aset by<br />
about 20%. On average, computing an overw<strong>at</strong>er mixing height increases<br />
these peak concentr<strong>at</strong>ions by about 3% to 6% from those obtained with the<br />
estim<strong>at</strong>ed heights.<br />
• Using either 0.5 m/s or 0.37 m/s for the minimum calcul<strong>at</strong>ed σ v has no effect<br />
on simul<strong>at</strong>ions of the three releases from the Gladsaxe tower in Denmark.<br />
<strong>The</strong> initial 7 km transport across this built-up area, plus the lack of a very<br />
stable overw<strong>at</strong>er boundary layer during these releases appears to promote<br />
computed σ v values <strong>at</strong> puff height th<strong>at</strong> exceed both of these minimums. For<br />
the Barseback, Sweden releases, using 0.37 m/s for the minimum σ v<br />
increases the arc-peak concentr<strong>at</strong>ions by 10% to 40% compared to results<br />
obtained with using 0.5 m/s. All of the releases from the Barseback tower<br />
experience little initial over land transport, and the air temper<strong>at</strong>ures on these<br />
days is significantly warmer than the Oresund temper<strong>at</strong>ures, producing a<br />
stable overw<strong>at</strong>er boundary layer.<br />
• None of these conclusions include an assessment of which of these choices<br />
performs best because in four of the nine experiments the results show a<br />
large overprediction tendency th<strong>at</strong> is well beyond the 10% to 40% changes<br />
noted above.<br />
Further consider<strong>at</strong>ion of the dispersion conditions captured in the Oresund<br />
experiments suggests th<strong>at</strong> turbulence advection, particularly in the offshore flow<br />
when the overw<strong>at</strong>er turbulence is much weaker than th<strong>at</strong> over land, must be explicitly<br />
simul<strong>at</strong>ed in order to improve performance. A test algorithm introduces this fe<strong>at</strong>ure<br />
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