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Linking GEOS-Chem with CMAQ: Consistency in meteorology and chemistry

Linking GEOS-Chem with CMAQ: Consistency in meteorology and chemistry. GEOS-Chem : Goddard Earth Observing System-CHEMisrty CMAQ : EPA ’ s Community Multiscale Air Quality modeling system. Daewon W. Byun, Nankyoung Moon, Heejin In, Chang-Keun Song.

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Linking GEOS-Chem with CMAQ: Consistency in meteorology and chemistry

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  1. Linking GEOS-Chem with CMAQ: Consistency in meteorology and chemistry GEOS-Chem: Goddard Earth Observing System-CHEMisrty CMAQ: EPA’s Community Multiscale Air Quality modeling system Daewon W. Byun, Nankyoung Moon, Heejin In, Chang-Keun Song Institute for Multidimensional Air Quality Studies (IMAQS) University of Houston Daniel Jacob, Rokjin Park Harvard University

  2. Introduction One of key problems of regional air quality models is finding accurate initial and boundary conditions (BCs) Most popular method is running a coarse regional model with fixed profiles for a reasonable period to spin-up the coarse domain, then use nesting for fine scale simulations. Profile BCs could be different at each side of domain reflecting certain regional differences but cannot account for changes caused by long-range air pollution transport events. • Key Issues linking global model output for regional models are differences in; • Chemical species • Scales and grid structure • - Spatial interpolation of global data for regional BC • 3. dynamic descriptions in Global and Regional Models

  3. Mechanics of Linkage • Chemical species:Currently, chemical mechanisms in global and regional models are not “consistent”: use species mapping MAPPING Table GEOS-CHEM O3-NOX-Hydrocarbon chemistry : 24 species CMAQ CB4 : 16 species Un-used species : ACET, ALD2

  4. Linkage of Chemistry GEOS-CHEM Mapping Table CMAQ SAPRAC-99

  5. Mechanics of Linkage • Linkage of scales: grid structures of the global and regional models are not “consistent” • Requires horizontal & vertical interpolation Implementation Example: Horizontal interpolation MODEL3 CMAQ(Multi-pollutant Air Quality model) GEOS-CHEM LAMBERT CONFORMAL 108 km X 108 km 23 layers in Sigma Po LAT-LON 2 degree X 2.5 degree 30 layers in Sigma P Initial & Boundary Condition IO/API Format in 108 km resolution Future – requires “geocentric” coordinates (from a flat-earth to a spherical earth, if not spheroid)

  6. Comparison of wind field MM5 NASA-GMAO General patterns of wind fields are well Some difference shows in circled area. - CMAQ/MM5 shows parallel to the grid - GEOS-CHEM/NASA-GMAO shows inflow This difference can be cause the uncertainty to regional air quality simulations. Let’s see how big the problem is:

  7. MM5 GMAO

  8. CMAQ O3 Boundary Flux (2wk avg, Aug 16-30, 2000) N S W E Solid: in-flux Dashed: out-flux GEOS_CHEM BC Profile BC

  9. Current Progress B.C. by Height: GEOS-CHEM 4 x 5 Vertical interpolation N W S E

  10. Current Progress B.C. by pressure: GEOS-CHEM 4 x 5 Vertical interpolation N W S E

  11. Current Progress Cf: B.C. by pressure : RAQMS 2 x 2.5 Vertical interpolation N W S E

  12. Comparison of CMAQ O3 with AIRS

  13. CMAQ vs. O3 RAOBS (GEOS-CB4 vs.Profile) Profile BC GEOS_CHEM BC GEOS-3

  14. Example with RAQMS: CMAQ/CB-4 vs. O3 RAOB met O3 STN021 Stratospheric O3 data assimilation issues: Chemistry and dynamics tropopause heights STN077 STN107 STN076 Note: other than Wallops island, the o3 zonde sites are different from those used in previous page

  15. What is the best method to link global/regional scale dynamics? Comparison of wind fields among four different MM5 results. ~ typical MM5 simulation for regional air quality study Case 1; MM5 results with EDAS first guess Case 2; MM5 results with EDAS first guess and GMAO objective analysis Case 3; MM5 results with GMAO, 36-km single domain Case 4; MM5 results with GMAO, 108/36-km nesting ~ trying to get closer wind fields to GMAO

  16. GMAO & MM5/Case-1 vs. RAOBs (wind components) 00z MM5/Case-1 GMAO

  17. Case 1&2 vs. GMAO (wind components) 00z Case 1 Case 2

  18. Case 3 & 4 vs. GMAO (wind components) 00z Case 3 Case 4 agreement with observation : CASE1> CASE2 > CASE4 > CASE3 agreement with GEOS-3 : CASE1 < CASE3 < CASE2 < CASE4 Is CASE2 the winner?

  19. Conclusion Studied chemical and meteorological consistency issues between the global and regional models. Conducted sensitivity CMAQ simulations with fixed profile data, GEOS-Chem BC, CB-4 and SAPRC99 mechanisms, and different MM5 outputs • Boundaries for global-regional scale linking must be located where direct emission sources are minimum; e.g., US-continental domain (Pacific to Atlantic Oceans). • Careful assessment of chemical species linkage and horizontal & vertical interpolation schemes required • Optimal mesoscale meteorological input obtained with EDAS first guess and GMAO objective analysis

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