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PRIME2_consequence_analysis_and _model_evaluation

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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.

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PRIME2_consequence_analysis_and _model_evaluation

  1. 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. 2. Outline 1. Consequence Analysis 2. Field Evaluation 3. Path Forward 4. Case Study 2 PRIME2 Consequence Analysis and Model Evaluation
  3. 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. 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. 5. Consequence Analysis PRIME2 Consequence Analysis and Model Evaluation5
  6. 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. 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. 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. 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. 10. Field Evaluation PRIME2 Consequence Analysis and Model Evaluation10
  11. 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. 12. Refined BPIP Method Example Bowline Point PRIME2 Consequence Analysis and Model Evaluation12
  13. 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. 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. 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. 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. 17. Refined BPIP Method Example Alaska North Slope PRIME2 Consequence Analysis and Model Evaluation17
  18. 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. 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. 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. 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. 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. 23. Alaska North Slope: Observed Values Max: 5.29 µg/m3 PRIME2 Consequence Analysis and Model Evaluation23
  24. 24. Alaska North Slope: AERMODv16216r Max: 4.48 µg/m3 PRIME2 Consequence Analysis and Model Evaluation24
  25. 25. Alaska North Slope: PRIME2v17234a Max: 13.20 µg/m3 PRIME2 Consequence Analysis and Model Evaluation25
  26. 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. 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. 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. 29. Case Study Comparison PRIME2 Consequence Analysis and Model Evaluation29
  30. 30. BPIP Values: AERMODv16216r H1H 24-hr avg = 78.9ug/m3 PRIME2 Consequence Analysis and Model Evaluation30
  31. 31. BPIP Values: PRIME2_17234a2 PRIME2 Consequence Analysis and Model Evaluation31 H1H 24-hr avg = 41.4ug/m3
  32. 32. EBD Values: AERMODv16216r PRIME2 Consequence Analysis and Model Evaluation32 H1H 24-hr avg = 39.5ug/m3
  33. 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. 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

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