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A. Guenther et al.
tive estimates of BVOC emissions. Although there have been advancements in the
procedures used to simulate BVOC emissions, there are still major uncertainties that
affect the reliability of air quality simulations. This includes significant gaps in our
understanding of BVOC emissions and their implementation in numerical models
including (1) isoprene emission factors, (2) missing compounds, and (3) and unrepresented processes including canopy heterogeneity and stress induced emissions.
In this study, we developed new emission factors and incorporated missing BVOC
compounds and unrepresented BVOC emission processes into the Model of Emissions of Gases and Aerosols from Nature (MEGAN) framework. To accomplish this,
we developed a transparent and comprehensive approach to assigning isoprene and
monoterpene emission factors and updated MEGAN to include additional BVOC and
processes including stress induced emissions and canopy heterogeneity. We evaluated MEGAN BVOC emission inventories for Texas and surrounding regions using
surface and aircraft observations and a photochemical model.
29.2 MEGAN Emission Factor Processor
One of the study objective was to develop a database system that provides a transparent approach for estimating BVOC emission factors. A transparent approach for
determining emission factors and other variables would facilitate efforts to assess and
improve biogenic emission models. An Emission Factor Processor for MEGAN3
(MEGAN-EFP) was developed as an open source Python code to ingest driving
variables and calculate landscape scale biogenic emission factors and other model
drivers. The approach is flexible so that users can use any available landcover and
emissions data and can investigate the performance of various datasets. A data quality
rating system was implemented so that the user can choose to omit low quality data.
The framework was implemented for BVOC emissions, specific leaf area and emission light dependence fraction and can be extended to include other plant and soil
traits that can vary spatially. The framework is illustrated in Fig. 29.1. The emission
factors calculated with the MEGAN-EFP are highly transparent in that the landcover
and emission data that they are based on can be traced back to specific publications.
29.3 Isoprene and Monoterpene Emission Factor Data
The MEGAN-EFP currently includes over 10,000 biogenic emissions measurements
from more than 200 studies. There are many other measurements published in the
literature and the database will be extended in the future and is expected to guide and
motivate new measurements that can fill gaps in the existing database. About half of
the isoprene and monoterpene emissions data in the MEGAN-EFP are from studies
that were conducted during the decades between 1960 and 2000 and are referred to
here as the Twentieth Century Emissions Database (TCED). The TCED is a synthe-
A. Guenther et al.
tive estimates of BVOC emissions. Although there have been advancements in the
procedures used to simulate BVOC emissions, there are still major uncertainties that
affect the reliability of air quality simulations. This includes significant gaps in our
understanding of BVOC emissions and their implementation in numerical models
including (1) isoprene emission factors, (2) missing compounds, and (3) and unrepresented processes including canopy heterogeneity and stress induced emissions.
In this study, we developed new emission factors and incorporated missing BVOC
compounds and unrepresented BVOC emission processes into the Model of Emissions of Gases and Aerosols from Nature (MEGAN) framework. To accomplish this,
we developed a transparent and comprehensive approach to assigning isoprene and
monoterpene emission factors and updated MEGAN to include additional BVOC and
processes including stress induced emissions and canopy heterogeneity. We evaluated MEGAN BVOC emission inventories for Texas and surrounding regions using
surface and aircraft observations and a photochemical model.
29.2 MEGAN Emission Factor Processor
One of the study objective was to develop a database system that provides a transparent approach for estimating BVOC emission factors. A transparent approach for
determining emission factors and other variables would facilitate efforts to assess and
improve biogenic emission models. An Emission Factor Processor for MEGAN3
(MEGAN-EFP) was developed as an open source Python code to ingest driving
variables and calculate landscape scale biogenic emission factors and other model
drivers. The approach is flexible so that users can use any available landcover and
emissions data and can investigate the performance of various datasets. A data quality
rating system was implemented so that the user can choose to omit low quality data.
The framework was implemented for BVOC emissions, specific leaf area and emission light dependence fraction and can be extended to include other plant and soil
traits that can vary spatially. The framework is illustrated in Fig. 29.1. The emission
factors calculated with the MEGAN-EFP are highly transparent in that the landcover
and emission data that they are based on can be traced back to specific publications.
29.3 Isoprene and Monoterpene Emission Factor Data
The MEGAN-EFP currently includes over 10,000 biogenic emissions measurements
from more than 200 studies. There are many other measurements published in the
literature and the database will be extended in the future and is expected to guide and
motivate new measurements that can fill gaps in the existing database. About half of
the isoprene and monoterpene emissions data in the MEGAN-EFP are from studies
that were conducted during the decades between 1960 and 2000 and are referred to
here as the Twentieth Century Emissions Database (TCED). The TCED is a synthe-