The Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN2.1): an extended and updated framework for modeling biogenic emissions

Abstract

The Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN2.1) is a modeling framework for estimating fluxes of 147 biogenic compounds between terrestrial ecosystems and the atmosphere using simple mechanistic algorithms to account for the major known processes controlling biogenic emissions. It is available as an offline code and has also been coupled into land surface models and atmospheric chemistry models. MEGAN2.1 is an update from the previous versions including MEGAN2.0 for isoprene emissions and MEGAN2.04, which estimates emissions of 138 compounds. Isoprene comprises about half of the estimated total global biogenic volatile organic compound (BVOC) emission of 1 Pg (1000 Tg or 10<sup>15</sup> g). Another 10 compounds including methanol, ethanol, acetaldehyde, acetone, α-pinene, β-pinene, <i>t</i>−β-ocimene, limonene, ethene, and propene together contribute another 30% of the estimated emission. An additional 20 compounds (mostly terpenoids) are associated with another 17% of the total emission with the remaining 3% distributed among 125 compounds. Emissions of 41 monoterpenes and 32 sesquiterpenes together comprise about 15% and 3%, respectively, of the total global BVOC emission. Tropical trees cover about 18% of the global land surface and are estimated to be responsible for 60% of terpenoid emissions and 48% of other VOC emissions. Other trees cover about the same area but are estimated to contribute only about 10% of total emissions. The magnitude of the emissions estimated with MEGAN2.1 are within the range of estimates reported using other approaches and much of the differences between reported values can be attributed to landcover and meteorological driving variables. The offline version of MEGAN2.1 source code and driving variables is available from <a href="http://acd.ucar.edu/~guenther/MEGAN/MEGAN.htm" target="_blank">http://acd.ucar.edu/~guenther/MEGAN/MEGAN.htm</a> and the version integrated into the Community Land Model version 4 (CLM4) can be downloaded from <a href="http://www.cesm.ucar.edu/" target="_blank">http://www.cesm.ucar.edu/</a>

Canopy level emissions of 2-methyl-3-buten-2-ol, monoterpenes, and sesquiterpenes from an experimental Pinus taeda plantation

“…Fluxes of BVOC were compared with MEGAN version 2.1 (Guenther et al, , 2012. MEGAN2.1 (referred to hereafter as MEGAN) is a commonly used modeling system to simulate landscape net emissions of VOC, CO, and NO from natural and agricultural landscapes.…”

“…CEE is the percentage of leaf emission of a given BVOC which escapes the canopy into the atmosphere above, and account for potential losses due to deposition and reactions with oxidants, primarily O 3 , NO 3 •, and OH•. These values range from approximately 10% for very reactive compounds such as β-caryophyllene to over 90% for the pinenes, isoprene and MBO (Stroud et al, 2005;Guenther et al, 2012). Since the (2) and (3)) used to describe the seasonal LAI pattern.…”

SOA Formation Potential of Emissions from Soil and Leaf Litter

“…To estimate the potential contribution of the soil and litter monoterpene emissions to total forest emissions, canopy monoterpene emission rates were modeled using MEGAN (v2.1beta). 16 Model input was selected based on reasonable values for comparison with measurements. Input meteorological values reflected fall and spring conditions at the sampling sitea time of year when leaf litter has the potential to significantly contribute to the total forest emissions.…”

“…14 Much effort has gone toward developing parametrizations of VOC emissions from vegetation sources, such as those contained in the model of emissions of gases and aerosols from nature (MEGAN). 15,16 While not considered a major global source of terpenoid emissions, soil and leaf litter still contribute significantly to VOCs in the atmosphere, particularly in spring and fall. 17,18 The research focus for soil and litter emissions has been primarily on methanol, acetone, acetaldehyde, and other VOCs with photoproducts that are too volatile to contribute significantly to SOA production.…”

Observations of Diurnal to Weekly Variations of Monoterpene-Dominated Fluxes of Volatile Organic Compounds from Mediterranean Forests: Implications for Regional Modeling

“…Global estimates of BVOC emissions from plants range from 1 to 1.5 Pg C yr −1 . 1 Mediterranean forest trees have been described as high BVOC emitters, 2−4 with emission depending primarily on light and temperature, and therefore being promoted by the warm Mediterranean climate. In the presence of sufficient sunlight and nitrogen oxides (NO x ), the oxidation of BVOCs can lead to the formation of tropospheric ozone, 5 a greenhouse gas with detrimental effects on plant health, crop yields, and human health.…”