Data and Code 

Which version of MEGAN should you use?

The code and input files are available for two versions of the MEGAN model. At the present time, most users should choose to use the MEGAN2.1 version. It is described by Guenther et al. 2012 (see and is widely used for regional to global modeling.  An older version, MEGAN2.04, is described by Guenther et al. 2006 (see and was initially released in 2007 on the UCAR Community Data Portal (   

The MEGAN2.1  User guide, code, driving variables and a test case are available for global simulations and for any region.  There is also a parallelized version with a description and performance benchmark available. Contact to request the parallelized MEGAN2.1 code.  

We are currently working on a new version, MEGAN3, that is illustrated in the above diagram. MEGAN3 is more transparent (e.g., the user can see the underlying data that are the basis for the emission factors at any given location) and more flexible (e.g., the user can easily modify the emission factors and other input variables) but this requires the use of domain specific inputs, rather than the use of the global default values of MEGAN2.1, to take advantage of this approach.  MEGAN3 is intended to be used for local (such as a specific urban area) to regional model simulations. We have applied the model in several urban US locations and have developed approaches to provide ultra high resolution (< 1 m) landcover and rapid surveying for urban vegetation emission factors in these areas. In contrast, MEGAN2.1 is not expected to work well in any urban area and can be highly uncertain for specific regions, especially where landcover and emission factor data were limited when MEGAN2.1 was developed. We have created global input files that will run MEGAN3 but they are based on the older MEGAN2.1 files and so are expected to perform similar to MEGAN2.1. They are intended to provide inputs in the regions surrounding a targeted city or region. If your focus is global modeling, or a region for which you have no domain specific input data, we recommend that you use MEGAN2.1. 

MEGAN3 has other improved (e.g., canopy model, light and temperature response algorithms, etc) and new (e.g., emission response to canopy depth, various stress responses) features but these features are under development and currently should be used only for sensitivity studies since the parameters in those stress response algorithms are only intended as placeholders that a user can vary to investigate the model sensitivity to these responses. An exception is the MEGAN3 drought and heat wave stress algorithm that is described by Wang et al. 2022 (see  

We are working on a MEGAN BVOC Emission Factor Encyclopedia to provide a comprehensive description of all available BVOC emission data (e.g., previous emission factor reviews, model databases, individual emission measurement studies) and how these data were synthesized to generate the MEGAN3 BVOC emission factors for individual plant species, genera and communities. This is intended to provide a clear understanding of how the emission factors were developed and also to indicate which emission factors are based on few or even no observations.

We have made the code and input data for MEGAN3.2 available for anyone interested but you should note that there is no MEGAN3 publication or User Guide and we are not able to provide any MEGAN3 support for the general public at this time.  We are working on finalizing MEGAN3 and expect to have a publication and User Guide available sometime in the near future. 

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