1. Office of Research and Development National Exposure Research Laboratory | Atmospheric Modeling and Analysis Division| A Tale of Two Models: A Comparison of the Biogenic Emission Inventory System (BEIS3.14) and Model of Emissions of Gases and Aerosols from Nature (MEGAN 2.04) George Pouliot 7 th Annual CMAS Conference 7 October 2008 What are the major differences in these two models that estimate emissions from biogenic sources? It was the best of times, it was the worst of times, it was the age of wisdom, …

2. Office of Research and Development National Exposure Research Laboratory | Atmospheric Modeling and Analysis Division | 1 1.Brief introduction to MEGAN and BEIS Biogenic Emissions Inventory System (BEIS v3.14) Model of Emissions of Gases and Aerosols from Nature (MEGAN v2.04) 2.Spatial differences between two models for an annual simulation 3.Temporal differences between the two models 4.Future Work Topics to be Discussed

3. Office of Research and Development National Exposure Research Laboratory |Atmospheric Modeling and Analysis Division | 2 Details about BEIS3.14 Based on BELD3 vegetation database (limited to North America) Emission factors derived for USGS land use types, crops, and specific tree types Soil NO algorithm is a function of temperature, rainfall, and growing season (Yienger and Levy, 1995) Simple canopy model for Light adjustment Summer/Winter factors based on freeze dates

4. Office of Research and Development National Exposure Research Laboratory |Atmospheric Modeling and Analysis Division | 3 Details about MEGANv2.04 Gridded emission factors based on global datasets for 11 species Emission factors for all other species based on 4 functional plant types (broadleaf, needles, shrubs, etc) NO emission estimates are a function of temperature only Simple parameterization of canopy light attenuation in Version 2.04; Version 2.10 will have an explicit canopy model Monthly gridded leaf area indices (LAIs) used for seasonal variation Guenther, A., T. Karl, et al. (2006). "Estimates of global terrestrial isoprene emissions using MEGAN (Model of Emissions of Gases and Aerosols from Nature)." Atmos. Chem. Phys. 6(11): 3181-3210.

5. Office of Research and Development National Exposure Research Laboratory |Atmospheric Modeling and Analysis Division | Isoprene Emissions(MG/yr) BEISMEGAN

6. Office of Research and Development National Exposure Research Laboratory |Atmospheric Modeling and Analysis Division | Monoterpenes Emissions (Mg/yr) BEISMEGAN Hot spot decrease

7. Office of Research and Development National Exposure Research Laboratory |Atmospheric Modeling and Analysis Division | Sesquiterpenes Emissions (Mg/yr) BEIS MEGAN

8. Office of Research and Development National Exposure Research Laboratory |Atmospheric Modeling and Analysis Division | Methanol Emissions (Mg/yr) BEISMEGAN

9. Office of Research and Development National Exposure Research Laboratory |Atmospheric Modeling and Analysis Division | Formaldehyde Emissions (Mg/yr) BEISMEGAN

10. Office of Research and Development National Exposure Research Laboratory |Atmospheric Modeling and Analysis Division | Soil Nitric Oxide BEISMEGAN

11. Office of Research and Development National Exposure Research Laboratory |Atmospheric Modeling and Analysis Division | 10 Summary of Spatial Differences Isoprene: Relative to BEIS, MEGAN generates higher isoprene in all areas, especially the southern U.S. Monoterpenes: MEGAN is lower in Canada, southwestern U.S., and northwestern U.S. Sesquiterpenes: MEGAN is lower in midwestern U.S. Methanol: MEGAN is higher in all areas Formaldehyde: MEGAN is lower in all areas, especially the southwestern U.S.

12. Office of Research and Development National Exposure Research Laboratory |Atmospheric Modeling and Analysis Division | 11 Percent Difference BEIS and MEGAN (based on 2003 annual emissions saprc99) + MEGAN is higher - BEIS is higher isoprene60% methanol139% monoterpenes-40% acetone12% sesquiterpenes-19% Nitric Oxide-72% Formaldehyde-71% OLE1-63% OLE2-37% RCHO-93% ALK1-92% ALK2-95% ALK3-63% ethene23% carbon monoxide-14%

13. Office of Research and Development National Exposure Research Laboratory | Atmospheric Modeling and Analysis Division | Isoprene 36km daily domain totals 2003

14. Office of Research and Development National Exposure Research Laboratory | Atmospheric Modeling and Analysis Division | Monoterpenes 36km daily domain totals 2003

15. Office of Research and Development National Exposure Research Laboratory | Atmospheric Modeling and Analysis Division | Sesquiterpenes 36km daily domain totals 2003

16. Office of Research and Development National Exposure Research Laboratory | Atmospheric Modeling and Analysis Division | Methanol 36km daily domain totals 2003

17. Office of Research and Development National Exposure Research Laboratory | Atmospheric Modeling and Analysis Division | Formaldehyde 36km daily domain totals 2003

18. Office of Research and Development National Exposure Research Laboratory | Atmospheric Modeling and Analysis Division | Soil Nitric Oxide 36km daily domain totals 2003

19. Office of Research and Development National Exposure Research Laboratory | Atmospheric Modeling and Analysis Division | 18 Summary Comparison of BEIS3.14 and MEGAN2.04 made for 2003 for SAPRC99 mechanism species MEGAN is higher for Isoprene, methanol, acetone, ethene BEIS is higher forMonoterpenes, sesquiterpenes, formaldehyde, other VOCs, soil NO BEIS has a more detailed soil NO algorithm MEGAN and BEIS have different spatial patterns (different normalized emission inputs)

20. Office of Research and Development National Exposure Research Laboratory | Atmospheric Modeling and Analysis Division | 19 Future Work Compare CMAQ results for BEIS3.14 and MEGAN2.04 for 3 week period in 2003 Incorporate MEGAN into CMAQ as an option compared to BEIS MEGANv2.10 is expected by the end of the year (will include updated canopy model) Eventually may replace BEIS with MEGAN Disclaimer: Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy