The Plume Rise Model Enhancements (PRIME) building downwash algorithms1 (Schulman et al. 2000) in AERMOD2 are being updated to address some of the most critical limitations in the current theory. These enhancements will incorporate the latest advancements related to building downwash effects. The technical aspects of these enhancements are discussed in more detail in a companion paper titled “PRIME2: Development and Evaluation of Improved Building Downwash Algorithms for Solid and Streamlined Structures (MO13)”. The updates to the PRIME code include new equations to account for building wake effects that decay rapidly back to ambient levels above the top of the building; reduced wake effects for streamlined structures; and reduced wake effects for high approach roughness. A consequence analysis comparing the current AERMOD/PRIME model versus the new AERMOD/PRIME2 model was performed. Additionally, a field data evaluation was conducted with the Bowline Point database. The results from these analyses are discussed below.

1. PRIME2 Consequence Analysis
and Model Evaluation
Guideline on Air Quality Models
The Changes
Chapel Hill, NC
Sergio A. Guerra, PhD
Ron Petersen, PhD, CCM
November 15, 2017
1

2. Outline
1. Consequence Analysis
2. Field Evaluation
3. Path Forward
4. Case Study
2 PRIME2 Consequence Analysis and Model Evaluation

3. 3
Key Features of PRIME2
• Building wake effects decay rapidly back to ambient levels above the
top of the building versus the current theory that has these effects
extending up to 3 building heights.
• Lateral dispersion enhancement in the wake is less than vertical
dispersion enhancement (current PRIME has them identical).
• The approach turbulence and wind speed is calculated at a more
appropriate height versus the current theory where half the wake
height at 15 building heights downwind of the building is used.
• Wake effects for streamlined structures are reduced.
• Wake effects decrease as approach roughness increases.
PRIME2 Consequence Analysis and Model Evaluation

4. 4
Project Summary
• Wind tunnel testing was performed to evaluate downwash effects from
rectangular and streamlined structures.
• CPP developed equations for predicting wind speed and turbulence in
building wakes for rectangular and streamlined structures based on wind
tunnel observations.
• CPP’s updates were compiled into a new AERMOD executable (PRIME2).
• Field versus model comparisons show that PRIME2 predictions are
generally within a factor of two of field observations but have a
overprediction tendency. Predictions also tend to be higher values than
with PRIME.
• Other theoretical problems have been identified. Correcting these may
alleviate the current overprediction tendency in PRIME2.
PRIME2 Consequence Analysis and Model Evaluation

5. Consequence Analysis
PRIME2 Consequence Analysis and Model Evaluation5

6. PRIME2 Consequence Analysis and Model Evaluation6
PRIME2_v17234a Evaluation
1:10:10 BDG with MakeMet Hs=1.2Hb
PRIME2_v17234a2
AERMOD_v16216r
zo=2cm zo=25cm zo=100cm
Max=173.0 ug/m3
Max=73.5 ug/m3
Max=132.9 ug/m3
Max=72.2 ug/m3 Max=79.0 ug/m3
Max=70.9 ug/m3

7. PRIME2 Consequence Analysis and Model Evaluation7
PRIME2_v17234a Evaluation
1:10:10 BDG with MakeMet Hs=1.5Hb
PRIME2_v17234a2
AERMOD_v16216r
zo=2cm zo=25cm zo=100cm
Max=130.1 ug/m3 Max=97.0 ug/m3 Max=53.2 ug/m3
Max=68.8 ug/m3 Max=69.1 ug/m3 Max=66.8 ug/m3

8. PRIME2 Consequence Analysis and Model Evaluation8
PRIME2_v17234a Evaluation
1:10:10 BDG with MakeMet Hs=2.5Hb
PRIME2_v17234a2
AERMOD_v16216r
zo=2cm zo=25cm zo=100cm
Max=37.2 ug/m3 Max=26.6 ug/m3 Max=23.1 ug/m3
Max=37.8 ug/m3 Max=35.6 ug/m3 Max=37.9 ug/m3

9. PRIME2 Consequence Analysis and Model Evaluation9
PRIME2_v17234a Evaluation
Bowline Point BDGs with Bowline Met Data
PRIME2_v17234a2
AERMOD_v16216r
Hs=1.33Hb=87.8m Hs=1.80Hb=117.4m Hs=2.50Hb=163.1m
Max=1013.1 ug/m3
Max=638.3 ug/m3 Max=279.9 ug/m3
Max=279.9 ug/m3
Max=192.2 ug/m3
Max=192.2 ug/m3
Max Observed = 823.5 ug/m3

10. Field Evaluation
PRIME2 Consequence Analysis and Model Evaluation10

11. Bowline Point Field Evaluation for Receptors 1 and 3
Q-Q Plot of Predicted vs. Observed Concs. with BPIP Values
Model Version
Top 25 Mean
X obs
Top 25 Mean
X predict
Top 25
Pre/Obs
Fractional
Bias
R1&3 AERMODv16216r (ug/m3) 422.17 447.71 1.06 0.06
R1&3 PRIME2v17234a (ug/m3) 422.17 684.51 1.62 0.47
PRIME2 Consequence Analysis and Model Evaluation11

12. Refined BPIP Method Example
Bowline Point
PRIME2 Consequence Analysis and Model Evaluation12

13. Refined BPIP Method Example: Bowline Point
Merged Tiers
Building
Dimensions
BPIP
(m)
Updated BPIP
(m)
Building Height(Hb) 65.23 65.23
Building Width (W) 121.95 121.95
Building Length (L) 109.93 35.98
XBADJ -127.62 -97.20
YBADJ -2.47 -2.5
Assumption 1:
Tallest tiers combine
(green bdg)
Assumption 2:
BDG WIDTH (W) is
crosswind width of
merged tier.
Assumption 3:
XBADJ starts at the
upwind edge of the
merged tier
Assumption 4:
BDG LENGTH (L) is
calculated by dividing
the area of the
merged tier by W
PRIME2 Consequence Analysis and Model Evaluation13

14. Refined BPIP Method Example: Bowline Point
Unmerged Tiers
Building
Dimensions
BPIP
(m)
Updated BPIP
(m)
Building Height(Hb) 65.23 65.23
Building Width (W) 94.57 49.9
Building Length (L) 130.27 27.65
XBADJ -132.56 -127.90
YBADJ -27.17 -4.0
Assumption 1:
Tallest tiers do not
combine (green bdg)
Assumption 2:
BDG WIDTH (W) is
crosswind width of
unmerged tier.
Assumption 3:
XBADJ starts at the
upwind edge of the
tallest tier
Assumption 4:
BDG LENGTH (L) is
calculated by dividing
the area of the tallest
tier by W
PRIME2 Consequence Analysis and Model Evaluation14

15. Bowline Point Field Evaluation for Receptors 1 and 3
Q-Q Plot of Predicted vs. Observed Concs. with BPIP Values
Model Version
Top 25 Mean
X obs
Top 25 Mean
X predict
Top 25
Pre/Obs
Fractional
Bias
R1&3 AERMODv16216r (ug/m3) 422.17 447.71 1.06 0.06
R1&3 PRIME2v17234a (ug/m3) 422.17 684.51 1.62 0.47
PRIME2 Consequence Analysis and Model Evaluation15

16. Model Version
Top 25 Mean
X obs
Top 25 Mean
X predict
Top 25
Pre/Obs
Fractional
Bias
R1&3 AERMODv16216r (ug/m3) 422.17 237.67 0.56 -0.56
R1&3 PRIME2v17234a (ug/m3) 422.17 535.01 1.27 0.24
Bowline Point Field Evaluation for Receptors 1 and 3
Q-Q Plot of Predicted vs. Observed Concs. with Modified BPIP Values
PRIME2 Consequence Analysis and Model Evaluation16

17. Refined BPIP Method Example
Alaska North Slope
PRIME2 Consequence Analysis and Model Evaluation17

18. Model Version
Top 25 Mean
X obs
Top 25 Mean
X predict
Top 25
Pre/Obs
Fractional Bias
AERMODv16216r 3.13 3.59 1.15 0.137
PRIME2_17234 3.13 7.58 2.42 0.829
Alaska North Slope Field Evaluation
Q-Q Plot of Predicted vs. Observed Concs. with BPIP Values
PRIME2 Consequence Analysis and Model Evaluation18

19. Building
Dimensions
BPIP
(m)
Updated BPIP
(m)
Building Height(Hb) 34.0 34.0
Building Width (W) 51.26 51.26
Building Length (L) 55.67 25.81
XBADJ -45.24 -43.70
YBADJ 6.58 6.6
Assumption 1:
Tallest tier combine
(green bdg)
Assumption 2:
BDG WIDTH (W) is
crosswind width of
merged tier.
Assumption 2:
XBADJ starts at the
lee edge of the
merged tier
Assumption 3:
YBADJ is calculated
by dividing the area
of the merged tier by
the width of the
artificially created
building
Refined BPIP Method Example: Alaska North Slope
Merged Tiers
PRIME2 Consequence Analysis and Model Evaluation19

20. Building
Dimensions
BPIP
(m)
Updated BPIP
(m)
Building Height(Hb) 34.0 34.0
Building Width (W) 52.98 20.25
Building Length (L) 28.61 25.30
XBADJ -28.7 -28.6
YBADJ -11.79 4.8
Assumption 1:
Tallest tier do not
combine (green bdg)
Assumption 2:
XBADJ starts at the
lee edge of the
merged tier
Assumption 3:
YBADJ is calculated
by dividing the area
of the merged tier by
the width of the
artificially created
building
Refined BPIP Method Example: Alaska North Slope
Unmerged Tiers
PRIME2 Consequence Analysis and Model Evaluation20

21. Model Version
Top 25 Mean
X obs
Top 25 Mean
X predict
Top 25
Pre/Obs
Fractional Bias
AERMODv16216r 3.13 3.59 1.15 0.137
PRIME2_17234 3.13 7.58 2.42 0.829
Alaska North Slope Field Evaluation
Q-Q Plot of Predicted vs. Observed Concs. with BPIP Values
PRIME2 Consequence Analysis and Model Evaluation21

22. Model Version
Top 25 Mean
X obs
Top 25 Mean
X predict
Top 25
Pre/Obs
Fractional Bias
AERMODv16216r 3.13 2.78 0.89 -0.120
PRIME2_17234 3.13 6.14 1.96 0.648
Alaska North Slope Field Evaluation
Q-Q Plot of Predicted vs. Observed Concs. with Modified BPIP Values
PRIME2 Consequence Analysis and Model Evaluation22

23. Alaska North Slope: Observed Values
Max: 5.29 µg/m3
PRIME2 Consequence Analysis and Model Evaluation23

24. Alaska North Slope: AERMODv16216r
Max: 4.48 µg/m3
PRIME2 Consequence Analysis and Model Evaluation24

25. Alaska North Slope: PRIME2v17234a
Max: 13.20 µg/m3
PRIME2 Consequence Analysis and Model Evaluation25

26. What Could be Causing Higher PRIME2 Predictions?
1. Streamline equations used in AERMOD are flawed. These equations are used as part
of the plume rise calculation in the wake region.
2. BPIP determined building dimension inputs are oftentimes incorrect. Refined
building dimension inputs result in better PRIME2 agreement with the Bowline Point
and Alaska North Slope field databases and reduce PRIME2 overprediction tendency.
3. EPA ORD work
1. The discontinuity between the cavity region and re-emitted plume was corrected by EPA ORD.
2. The wind speed used to calculate concentrations was corrected by EPA ORD. This problem is
likely causing some of the PRIME2 overprediction tendency.
3. Cap on ambient turbulence levels has been corrected by EPA ORD.
26

27. Other Pending Issues
1. Location mismatch in cavity region. For buildings with multiple stacks, PRIME places
all stacks impacts (regardless of their location), at the building center. This results in
an overlap of all maximum concentrations at the same location in the cavity region.
2. Wake effects for porous and platform structures need to be addressed.
27

28. Implementation Process
CPP and ORD
Submittals to
EPA OAQPS
Journal
Articles
Published
OAQPS Codes
CPP and ORD
Enhancements
EPA releases
New PRIME
as Alpha
option
EPA
releases
PRIME as
Beta
option
Notice of
proposed
rulemaking
(NPRM)
New PRIME
is released
as default
regulatory
option
Alternative refined model requirements in App W, Section 3.2.2 include:
1-Model has received a scientific peer review;
2-Model can be demonstrated to be applicable to the problem on a theoretical basis;
3-The data bases to perform analysis are available and adequate;
4-Appropriate performance evaluations show model is not biased toward underestimation; and
5-A protocol on methods and procedures to be followed has been established
28 PRIME2 Consequence Analysis and Model Evaluation

29. Case Study Comparison
PRIME2 Consequence Analysis and Model Evaluation29

30. BPIP Values: AERMODv16216r
H1H 24-hr avg = 78.9ug/m3
PRIME2 Consequence Analysis and Model Evaluation30

31. BPIP Values: PRIME2_17234a2
PRIME2 Consequence Analysis and Model Evaluation31
H1H 24-hr avg = 41.4ug/m3

32. EBD Values: AERMODv16216r
PRIME2 Consequence Analysis and Model Evaluation32
H1H 24-hr avg = 39.5ug/m3

33. Conclusions
• PRIME2 includes a superior theory to account for building
downwash effects for rectangular and streamlined structures.
• Benefits from improved theory cannot be fully realized due to
outstanding issues in the model.
• Work from EPA ORD complements the work performed by
CPP.
• Plan is to continue EPA collaboration to address model
improvements to AERMOD related to building downwash.
PRIME2 Consequence Analysis and Model Evaluation33

34. Sergio A. Guerra, PhD Ron Petersen, PhD, CCM
sguerra@cppwind.com rpetersen@cppwind.com
Mobile: + 612 584 9595 Mobile:+1 970 690 1344
wwww.SergioAGuerra.com
CPP, Inc.
2400 Midpoint Drive, Suite 190
Fort Collins, CO 80525
+ 970 221 3371
www.cppwind.com @CPPWindExperts
Questions?
34 PRIME2 Consequence Analysis and Model Evaluation