2011 10 07 (uam) emadrid aortigosa uam estilos aprendizaje sistemas adaptativos enseñanza
Session 9, Unit 17 UAM and CAMx
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Transcript of Session 9, Unit 17 UAM and CAMx
Session 9, Unit 17
UAM and CAMx
UAM and CAMx
UAM - Urban Airshed Model Currently available versions:
UAM-V 1.24 UAM-V 1.30 Available from Systems Applications International
(SAI)
CAMx - Comprehensive Air quality Model with extension Version 3.00 Available from ENVIRON
UAM and CAMx
Multi-scale, three dimensional photochemical grid modelsMost applications in urban or regional ozone modelingUsed for planning (e.g., SIP, search for control strategies)Similar in many aspectsComparison Comparative study of two ozone episodes in the
eastern US commissioned by Ohio EPA (June 1997)
UAM and CAMx
Results: small differences
CAMx
Grid modelProcesses modeled in each grid cell volume Emission Dispersion Chemical reactions Removal (wet and dry)
CAMx
Fundamental equation – Eulerian continuity equation for each chemical species
VH – Horizontal wind vector - Net vertical entrainment rate h – Layer interface height K – Turbulent exchange coefficient
Horizontal
Advection
Vertical transport
Turbulent diffusion
CAMx
Nested Grid Coarse grid to cover a region Fine grid to model details of urban areas
Plume-in-Grid (PiG) Track individual plumes of large sources in
grid cell using Lagrangian module until the plume grow large enough to be adequately represented in the grid model (otherwise, pollutants are considered to be distributed uniformly within a grid cell)
CAMx PiG illustration
Source: CAMx User’s Guide by ENVIRON
CAMx
Ozone Source Apportionment Technology (OSAT) Track contributions to ozone
concentration in a grid cell by source category or region
Make evaluation of NOx and VOC controls easy
CAMx
Chemical reactions Five sets of chemical mechanisms
based on the Carbon Bond Mechanism version 4 (CBM-IV) or the SAPRC97 mechanism
Large number of reactions in each mechanism CBM-IV: 96 reactions SAPRC97: 184 reactions
CAMx
Example (SAPRC97)
…
From lookup table
generated by Photolysis
Preprocessor
Source: CAMx User’s Guide by ENVIRON
CAMx
Solved using numerical integration Consumes largest portion of CPU time “Adaptive-hybrid” approach results in
ten-fold speedup in chemical solution (factor of 3-4 for overall model)
Chemical Mechanism Compiler (CMC) – automatically generate FORTRAIN code for the chemistry solver for selected chemical mechanism (CMC is for internal use, not distributed with CAMx)
CAMx
Photolysis TUV ratiative transfer and photolysis
model developed by NCAR Multi-dimensional lookup tale of
photolytic rates by surface albedo, total ozone column, haze turbidity, altitude, and zenith angle
The photolytic rates can be adjusted by cloud cover
CAMx
Decoupled Direct Method (DDM) For sensitivity analysis Wider applicability than OSAT
CAMx
Data requirements Run control file Chemistry parameters
file Photolysis rate file Albedo/haze/ozone file
(AHO file) Top concentration file Land use file Met files
(height/pressure, wind, temp.,water vapor, cloud cover, rainfall, & diffusivity)
Files for initial & boundary conditions
Source files
Source: CAMx User’s Guide by ENVIRON
CAMx
Running CAMx Compile source code (specify
computer platform)
CAMx Computer resource requirements
Source: CAMx User’s Guide by ENVIRON
CAMx
Evaluation of control strategy
Source: CAMx User’s Guide by ENVIRON
Case1: Initial VOC/NOx=10:1
CAMx
Source: CAMx User’s Guide by ENVIRON
Case1: VOC/NOx=10:1
CAMx
Source: CAMx User’s Guide by ENVIRON
Case2:Initial VOC/NOx=20:1
CAMx
Source: CAMx User’s Guide by ENVIRON
Case 3: Initial VOC/NOx=5:1
Session 9, Unit 18
Final Review