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) 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, …

George Pouliot 7 th Annual CMAS Conference 7 October 2008 Office of Research and Development

National Exposure Research Laboratory | Atmospheric Modeling and Analysis Division|

Topics to be Discussed

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Brief introduction to MEGAN and BEIS

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Biogenic Emissions Inventory System (BEIS v3.14) Model of Emissions of Gases and Aerosols from Nature (MEGAN v2.04) Spatial differences between two models for an annual simulation Temporal differences between the two models Future Work Office of Research and Development

National Exposure Research Laboratory | Atmospheric Modeling and Analysis Division |

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Details about BEIS3.14

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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 Office of Research and Development

National Exposure Research Laboratory |Atmospheric Modeling and Analysis Division |

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Details about MEGANv2.04

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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.

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BEIS

Isoprene Emissions(MG/yr)

MEGAN

Biogenic Isoprene Anthropogenic Isoprene Other Biogenic VOCs Other Anthropogenic VOCs

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BEIS

Monoterpenes Emissions (Mg/yr)

MEGAN Hot spot decrease

Biogenic Monoterpenes Anthropogenic monoterpenes Other Biogenic VOCs Other Anthropogenic VOCs

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BEIS

Sesquiterpenes Emissions (Mg/yr)

MEGAN

Biogenic sesquiterpenes Anthropogenic sesquiterpenes Other Biogenic VOCs Other Anthropogenic VOCs

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BEIS

Methanol Emissions (Mg/yr)

MEGAN

16% 16% 0% Biogenic Methanol Anthropogenic Methanol Other Biogenic VOCs Other Anthropogenic VOCs

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Formaldehyde Emissions (Mg/yr)

BEIS MEGAN

19% 2% 0% Biogenic formaldehyde Anthropogenic formaldehyde Other Biogenic VOCs Other Anthropogenic VOCs

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Soil Nitric Oxide

BEIS MEGAN

Anthropogenic Nox Biogenic Nox

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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.

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Percent Difference BEIS and MEGAN

(based on 2003 annual emissions saprc99) isoprene methanol monoterpenes acetone sesquiterpenes Nitric Oxide Formaldehyde OLE1 OLE2 RCHO ALK1 ALK2 ALK3 ethene carbon monoxide

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+ MEGAN is higher - BEIS is higher 11

Isoprene 36km daily domain totals 2003

DAILY DOMAIN WIDE ISOPRENE FLUX

4500 4000 3500 3000 2500 2000 1500 1000 500 0 1 21 41 61 81 101 121 141 161 181 201 221 241 261 281 301 321 341 361

DAY OF THE YEAR

MEGAN

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Monoterpenes 36km daily domain totals 2003

DAILY MONOTERPENES DOMAIN WIDE EMISSION FLUX

600000 500000 400000 300000 200000 100000 0 1 22 43 64 85 106 127 148 169 190 211 232 253 274 295 316 337 358

DAY OF YEAR

MEGAN BEIS

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50000 45000 40000 35000 30000 25000 20000 15000 10000 5000 0 1 22 43 64 85 106 127 148 169 190 211 232 253 274 295 316 337 358

DAY OF YEAR

MEGAN BEIS

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3000 2500 2000 1500 1000 500 0 1 21 41 61 81 101 121 141 161 181 201 221 241 261 281 301 321 341 361

DAY OF YEAR

MEGAN BEIS

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Formaldehyde 36km daily domain totals 2003

DAILY DOMAIN WIDE FORMALDEHYDE FLUX

300 250 200 150 100 50 0 1 21 41 61 81 101 121 141 161 181 201 221 241 261 281 301 321 341 361

DAY OF THE YEAR

MEGAN

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250000 200000 150000 100000 50000 0 1 22 43 64 85 106 127 148 169 190 211 232 253 274 295 316 337 358

DAY OF THE YEAR

MEGAN BEIS

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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)

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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

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