Megan emission factor is different between v3.2 and v2.1

Hi everyone,

When running the megan model, I noticed v2.1’s EF is classified according to CLM-PFT, the EFv210806.csv file of v3.2 also contains CLM-PFT: 1-15. However, I observed significant differences in the magnitude of EF values between v3.2 and v2.1. Initially, I thought this difference was due to unit conversion (The units for v3.2 are unknown while v2.1 use ug m-2 h-1), but the relationship between the two is not proportional. What could be the reason for this discrepancy?

If I want to add a new tree species (Pinus massoniana) to the EFv210806.csv in megan3.2, and the EF units provided in the literature are μg C g−1 hr−1, what conversion method should I use to add the EF to EFv210806.csv?

Thank you very much for your help
Figures 1 shows the emission factors for v2.1, while Figures 2 and 3 represent the emission factors for v3.2, which are identical.

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Hi @liuhao,

Thank you for sharing this finding. Unfortunately, this question is upstream of the MEGAN code used in CMAQ. The MEGAN 3.2 preprocessor is developed by Alex Guenther ( and his team. He is not active on this forum so I recommend emailing him directly.


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