Volume 1 - The Atmospheric Studies Group at TRC

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3.2 CALPUFF Platform Downwash The existing CALPUFF Huber-Snyder/Schulman-Scire (HS/SS) downwash modules are used to model downwash effects due to elevated structures by using that portion of the structure that is “solid”. A platform height (z plat ) is added to the list of variables that describe the effective building dimensions The effective building width H w and building height H b are prepared for each of 36 wind directions (10- degree intervals) by neglecting the gap below z plat . That is, the structure is defined as if the solid portion rests on the “ground”, and the EPA Building Profile Input Program (BPIP) can be used to develop the direction-specific effective height and width. Any point-source emission released on or near the structure is prescribed using the full release height h s above the “ground”, not the height above the platform deck. The full release elevation above ground is adjusted by subtracting the platform height prior to any tests that define the downwash potential (e.g., the 2.5 building-height rule for GEP), and any downwash plume enhancements that depends on the effective stack height. This adjusted stack height is not used as the physical release height in any other calculations. The Huber-Snyder (Huber and Snyder, 1976; Huber, 1977) technique is used for h − z > H + T L (3-36) s plat b bd b where L b is the lesser of the effective building height and width, and T bd has a default value of 0.5. A negative value of T bd indicates the Huber-Snyder method is used for all stacks, and a value of 1.5 results in the Schulman-Scire (Scire and Schulman, 1980; Schulman and Hanna, 1986) method always being used. If T Tb is set equal to 0.5 (its default value), the CALPUFF treatment will be equivalent to that in ISC3. When the Huber-Snyder technique is used, the first step is to compute the effective plume height H e due to momentum rise at a downwind distance of 2 H b . This rise uses the wind speed at the full stack height, h s . If (H e –z plat ) exceeds H b + 1.5 L b , building downwash effects are assumed to be negligible. Otherwise, buildinginduced enhancement of the plume dispersion coefficients is evaluated. For adjusted stack heights h s –z plat less than 1.2H b , both σ y and σ z are enhanced. Only σ z is enhanced for adjusted stack heights above 1.2 H b (but below H b + 1.5 L b ). Enhancements to σ y and σ z are not functions of h s or h s -z plat . When the Schulman-Scire technique is used, a linear decay factor is applied to the building-induced enhancement of the vertical dispersion coefficient, and plume rise is Final Report Vol.1 16
adjusted to account for the effect of downwash. The plume rise equations are not functions of h s or h s -z plat . The linear decay factor for σ z is determined as: σ ′ z = A σ ′ z (3-37) where σ ′ z is determined from the HS downwash equations, and ⎧1 ⎪ H A = ⎨ ⎪ ⎪ ⎩0 b − ( H e 2L b − z plat ) + 1 H b < ( H H b e H − z e + 2L plat b ≤ ( H ) ≤ H < ( H b e − z b plat ) + 2L − z plat b ) (3-38) AERMOD Turbulence Profile Option The turbulence velocity for horizontal fluctuations is computed from contributions from shear and buoyancy. The total turbulence velocity is obtained by summing the component variances: σ = σ + σ (3-39) v 2 vs 2 vb The shear component is modeled with a variance that is a maximum at the ground (σ vs 2 =3.6u * 2 ), and decreases linearly through the depth of the mechanically mixed layer to a residual value of 0.25 m 2 /s 2 , if this residual value is less than the value at the ground. If the residual value is larger, the value at the ground is used for all heights. The buoyancy component is constant (σ vb 2 =0.35w * 2 ) up to z i , and decreases linearly to the residual value at 1.2z i . Again, the value at the ground is used at all heights if it is less than the residual value. The turbulence velocity for vertical fluctuations is also computed from shear and buoyancy contributions. The buoyancy component of the variance is computed as: 2 wb 2 * 3 σ = 1.6w ( z z ) 2 / ( z ≤ 0.1z ) (3-40) 2 wb i i 2 σ = 0.35w ( z = 0.1z to z ) (3-41) 2 wb * i i 2 −6( z−z ) zi σ = 0.35w e i ( z > z ) (3-42) * i The shear component has both a surface-driven contribution (from u * ) and a residual contribution from turbulence aloft that is assumed to have an intensity of order 2% of the wind speed at z i : 2 ws 2 * 2 σ = 1.3u (1 − z z ) + (0.02 u z / z ) ( z ≤ z ) (3-43) i zi i i Final Report Vol.1 17
Page 1 and 2: Development of the Next Generation
Page 3 and 4: 1. INTRODUCTION The purpose of this
Page 5 and 6: • Prognostic Meteorological Model
Page 7 and 8: o 1: Maul (1980)-Carson (1973) o 2:
Page 9 and 10: into 50 tiles (90 RUC grid-points/t
Page 11 and 12: y H ( 1− 34.15z / L) 1/ 3 = (3-9)
Page 13 and 14: During execution, the bulk algorith
Page 15 and 16: Anemometer Height Adjustment for La
Page 17: T (ºK) g (m/s 2 ) temperature grav
Page 21 and 22: Two methods of supplying the timesc
Page 23 and 24: cell is the cell that determines th
Page 25 and 26: June 4 (1130-1230 CET) L. Turbulenc
Page 27 and 28: 4. MODEL PERFORMANCE EVALUATION 4.1
Page 29 and 30: The CALMET preprocessors TERREL, CT
Page 31 and 32: All sampler locations are used as r
Page 33 and 34: Table 4-2b Over-water Meteorologica
Page 35 and 36: Meteorological data used in the OCD
Page 37 and 38: . . CARPINTERIA, CA 3814 . UTM Nort
Page 39 and 40: Year Month Day Table 4-4 Over-water
Page 41 and 42: Datum: NAS-C (North American 1927)
Page 43 and 44: Table 4-5 Source Characterization f
Page 45 and 46: Table 4-6a Over-water Meteorologica
Page 47 and 48: Geophysical Processing Gridded land
Page 49 and 50: Table 4-7 Source Characterization f
Page 51 and 52: tape format called GF-3. These data
Page 53 and 54: . . Strait of Oresund 6230 6220 UTM
Page 55 and 56: . . Strait of Oresund 6230 6220 UTM
Page 57 and 58: Table 4-10 SEA.DAT Meteorological D
Page 59 and 60: the numbers refer to ICOARE values,
Page 61 and 62: that are simulated during the one-h
Page 63 and 64: 4.3 Evaluation Results Cameron, Car
Page 65 and 66: improve model performance relative
Page 67 and 68: Figure 4-7. Graphical depiction of
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Figure 4-8. Graphical depiction of
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Page 73 and 74:
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Table 4-15 Performance Statistics f
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Performance of CALPUFF Configuratio
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Table 4-16 (continued) Performance
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into CALPUFF, and the simulations a
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Table 4-18 Oresund Results with Min
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Table 4-20 Oresund Results with Min
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4.4 Recommendations A minimum σ v
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SEA.DAT and OZONE.DAT files are pro
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36 34 32 30 Latitude 28 26 24 22 -1
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WMO Number WBAN Number Station Iden
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36 72363 72340 34 72249 72248 72235
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36 34 32 41008 30 42035 42007 42040
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36 34 32 30 Latitude 28 26 24 22 -1
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COOP State Station Name Table 5-4.
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COOP State Station Name Table 5-4.
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Table 5-4. (Concluded) Hourly NWS P
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Table 5-5. Ozone Stations Station I
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Table 5-5. (Continued) Ozone Statio
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Table 5-5. (Continued) Ozone Statio
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36 317 339 361 383 405 427 449 471
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- Figure 5-8. “Inputs/Outputs & R
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6. REFERENCES Batchvarova, E. and S
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Maat, N., C. Kraan, and W.A. Oost,
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APPENDIX: COMPILATION OF A HIGH RES
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Volume 1 - The Atmospheric Studies Group at TRC

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