1 / 22

Session 9, Unit 17 UAM and CAMx

Session 9, Unit 17 UAM and CAMx. UAM and CAMx. UAM - U rban A irshed M odel Currently available versions: UAM-V 1.24 UAM-V 1.30 Available from Systems Applications International (SAI) CAMx - C omprehensive A ir quality M odel with e x tension Version 3.00 Available from ENVIRON.

aric
Download Presentation

Session 9, Unit 17 UAM and CAMx

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Session 9, Unit 17UAM and CAMx

  2. 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

  3. UAM and CAMx • Multi-scale, three dimensional photochemical grid models • Most applications in urban or regional ozone modeling • Used for planning (e.g., SIP, search for control strategies) • Similar in many aspects • Comparison • Comparative study of two ozone episodes in the eastern US commissioned by Ohio EPA (June 1997)

  4. UAM and CAMx • Results: small differences

  5. CAMx • Grid model • Processes modeled in each grid cell volume • Emission • Dispersion • Chemical reactions • Removal (wet and dry)

  6. 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 Vertical transport Horizontal Advection Turbulent diffusion

  7. 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)

  8. CAMx • PiG illustration Source: CAMx User’s Guide by ENVIRON

  9. 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

  10. 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

  11. CAMx • Example (SAPRC97) … From lookup table generated by Photolysis Preprocessor Source: CAMx User’s Guide by ENVIRON

  12. 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)

  13. 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

  14. CAMx • Decoupled Direct Method (DDM) • For sensitivity analysis • Wider applicability than OSAT

  15. 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

  16. CAMx • Running CAMx • Compile source code (specify computer platform)

  17. CAMx • Computer resource requirements Source: CAMx User’s Guide by ENVIRON

  18. CAMx Case1: Initial VOC/NOx=10:1 • Evaluation of control strategy Source: CAMx User’s Guide by ENVIRON

  19. CAMx Case1: VOC/NOx=10:1 Source: CAMx User’s Guide by ENVIRON

  20. CAMx Case2: Initial VOC/NOx=20:1 Source: CAMx User’s Guide by ENVIRON

  21. CAMx Case 3: Initial VOC/NOx=5:1 Source: CAMx User’s Guide by ENVIRON

  22. Session 9, Unit 18Final Review

More Related