Model of Emissions of Gases and Aerosols from Nature (MEGAN)

MEGAN is a modeling system for estimating the net emission of gases and aerosols from terrestrial ecosystems into the atmosphere. Driving variables include landcover, weather, and atmospheric chemical composition. MEGAN is a global model with a base resolution of ~ 1 km and so is suitable for regional and global models. A FORTRAN code is available for generating emission estimates for the CMAQ regional air quality model. The algorithms have also been incorporated as an on-line component in several regional and global chemistry and transport models. Global distributions of landcover variables (Emission Factors, Leaf Area Index, and Plant Functional Types) are available for spatial resolutions ranging from ~ 1 to 100 km and in several formats (ARCGIS, netcdf).

User Guides:

1. FORTRAN code User Guide: Describes how to download and run a FORTRAN code that generates biogenic emission estimates for CMAQ.

2. Data Portal User Guide: Describes how to access the code and input data.

3. Input Data Preprocessor User Guide: Describes how to regrid the landcover input data for a specific model domain using a GIS.

MEGAN versions:

We have assigned version numbers to the MEGAN FORTRAN code as well as the input data.

The current version of the FORTRAN code is v2.04 (released October 29, 2007)

The current version of the landcover data include

• Leaf Area Index version 2.0
• Plant Functional Type version 2.1
• Emission Factors verison 2.1

Any of the landcover datasets (i.e. version 2.0 or version 2.1) can be used as inputs for the FORTRAN code v2.04.

MEGAN Publications:

• Guenther et al., J. Geophys. Res., 104, 30625-30639 (1999): This manuscript describes the canopy environment model used in MEGAN.
• Guenther et al., ACP 6, 3181-3210 (2006). Also read the Corrigendum which corrects typographical errors in some equations. This manuscript describes MEGAN isoprene emission algorithms, emission factors and landcover data.
• Helmig, D., J. Ortega, T. Duhl, D. Tanner, A. Guenther, P. Harley, C. Wiedinmyer, J. Milford, T. Sakulyanontvittaya, Sesquiterpene emissions from pine trees- Identifications, emission rates and flux estimates for the contiguous United States, Environ. Sci. Tech., 41, 1545-1553, 2007. This manuscript describes regional sesquiterpene distributions estimated using MEGAN.
• Ortega, J., D. Helmig, A. Guenther, P. Harley, S. Pressley, and Christoph Vogel, Flux estimates and OH reaction potential of reactive biogenic volatile organic compounds (BVOCs) from a mixed northern hardwood forest, Atmos. Environ., 41, 5479-5495, 2007. This manuscript describes an application of a canopy scale version of MEGAN.
• Donkelaar, A., R. Martin, R. Park, C. Heald, T.-M. Fu, A. Guenther, Model evidence for a significant source of secondary organic aerosol from isoprene, Atmospheric Environment , 41, 1267-1274, 2007. MEGAN used to estimate biogenic VOC emissions.
• Guenther et al. Atmospheric Environment (in preparation for Atmos. Environ 50th anniversary special issue). This manuscript describes MEGAN emission algorithms and emission factors for compounds other than isoprene.
• Sakulyanontvittaya et al. submitted to Environ. Science and Technology. This manuscript investigates the sensitivity of MEGAN emission estimates to the monoterpene and sesquiterpene parameters.

Contact Alex Guenther (guenther@ucar.edu) with questions or suggestions regarding MEGAN