# MEGAN **URL:** https://forum.cmascenter.org/c/megan/56.md [Latest](https://forum.cmascenter.org/latest.md) · [Categories](https://forum.cmascenter.org/categories.md) · [Tags](https://forum.cmascenter.org/tags.md) --- ## [About the MEGAN category](https://forum.cmascenter.org/t/about-the-megan-category/1808)
**Author:** [@lizadams](https://forum.cmascenter.org/u/lizadams)\ **Replies:** 1\ **Last updated:** [March 14, 2023, 2:29pm UTC](https://forum.cmascenter.org/t/about-the-megan-category/1808 "2023-03-14T14:29:28Z")
Category for those who would like to collaborate on solving issues regarding MEGAN. Note, MEGAN support is primarily addressed through the developers at University of California Irvine. Obtain the code: User Manual… --- ## [MEGAN v3.2: How Should Ecotype Data Be Defined for Regional Applications?](https://forum.cmascenter.org/t/megan-v3-2-how-should-ecotype-data-be-defined-for-regional-applications/6267)
**Author:** [@bb404bb](https://forum.cmascenter.org/u/bb404bb)\ **Replies:** 1\ **Last updated:** [August 12, 2026, 3:15pm UTC](https://forum.cmascenter.org/t/megan-v3-2-how-should-ecotype-data-be-defined-for-regional-applications/6267 "2026-08-12T15:15:15Z")
Hello everyone, I am currently trying to use MEGAN v3.2. I have mostly understood the general workflow and am now able to generate BVOC emissions for use in the CMAQ model. However, I am still unclear about the Ecotype… --- ## [MEGAN3.2 lai or laiv input data](https://forum.cmascenter.org/t/megan3-2-lai-or-laiv-input-data/4720)
**Author:** [@liuhao](https://forum.cmascenter.org/u/liuhao)\ **Replies:** 4\ **Last updated:** [June 3, 2026, 6:10pm UTC](https://forum.cmascenter.org/t/megan3-2-lai-or-laiv-input-data/4720 "2026-06-03T18:10:16Z")
Hi everyone, I’m currently trying to run MEGAN 3.2. I’ve noticed on the official website it mentions that “MEGAN 3.2 will accept either LAI or LAIv”. So, for Leaf Area Index data, can I convert MCD15A2H data to nc form… --- ## [MEGAN32 Preprocessing Issues](https://forum.cmascenter.org/t/megan32-preprocessing-issues/6188)
**Author:** [@Tend](https://forum.cmascenter.org/u/Tend)\ **Replies:** 2\ **Last updated:** [May 22, 2026, 6:23am UTC](https://forum.cmascenter.org/t/megan32-preprocessing-issues/6188 "2026-05-22T06:23:16Z")
Hello, I am encountering some issues while attempting to calculate biogenic emissions using the online MEGAN module within CMAQ 5.4. I have successfully generated various CSV and NetCDF files—such as CT3\*, FERT\*, LANDTYP… --- ## [MEGAN preprocessor does not exist](https://forum.cmascenter.org/t/megan-preprocessor-does-not-exist/6164)
**Author:** [@Ominde](https://forum.cmascenter.org/u/Ominde)\ **Replies:** 1\ **Last updated:** [March 23, 2026, 1:36pm UTC](https://forum.cmascenter.org/t/megan-preprocessor-does-not-exist/6164 "2026-03-23T13:36:57Z")
Hello, everyone. This page \[ https://bai.ess.uci.edu/megan/data-and-code/megan32 \] does not exist now, which offers the source code of MEGAN preprocessor, like prepmegan4cmaq\_grwform.f90. I have downloaded the code and… --- ## [Problem with METCRO2D using MEGAN inline](https://forum.cmascenter.org/t/problem-with-metcro2d-using-megan-inline/6138)
**Author:** [@MariaMB](https://forum.cmascenter.org/u/MariaMB)\ **Replies:** 3\ **Last updated:** [January 22, 2026, 4:34pm UTC](https://forum.cmascenter.org/t/problem-with-metcro2d-using-megan-inline/6138 "2026-01-22T16:34:08Z")
Hello! I’m using MEGAN inline in CMAQ version 5.4. I’ve used “prepmegan4cmaq” to prepare my input files and I’m getting the following error, related to my MCIP (v5.4) METCRO2D file: Value for PROMPTFLAG: T returning TR… --- ## [MEGAN v3.2 megvea error with NLAI](https://forum.cmascenter.org/t/megan-v3-2-megvea-error-with-nlai/5695)
**Author:** [@Heomin](https://forum.cmascenter.org/u/Heomin)\ **Replies:** 3\ **Last updated:** [December 3, 2025, 10:03am UTC](https://forum.cmascenter.org/t/megan-v3-2-megvea-error-with-nlai/5695 "2025-12-03T10:03:47Z")
Hi CMAS users, I am trying to generate BVOC emissions using MEGANv3.2. As I understand, the NLAI value can be set to either 46 or 12 in the megvea program and all related tools. I was able to successfully generate BVO… --- ## [MEGAN output unit conversion: from mol/s to g/s](https://forum.cmascenter.org/t/megan-output-unit-conversion-from-mol-s-to-g-s/5886)
**Author:** [@tingting1](https://forum.cmascenter.org/u/tingting1)\ **Replies:** 1\ **Last updated:** [July 23, 2025, 2:04pm UTC](https://forum.cmascenter.org/t/megan-output-unit-conversion-from-mol-s-to-g-s/5886 "2025-07-23T14:04:57Z")
Hi, Can the compound units output by megan based on the CB05 mechanism be converted from mol/s to g/s using the relative molecular mass recommended by Specdb for the CB05 mechanism, or should a different relative molecu… --- ## [FERT\_CONUS.nc Units](https://forum.cmascenter.org/t/fert-conus-nc-units/5852)
**Author:** [@gpara35](https://forum.cmascenter.org/u/gpara35)\ **Replies:** 2\ **Last updated:** [July 4, 2025, 7:55pm UTC](https://forum.cmascenter.org/t/fert-conus-nc-units/5852 "2025-07-04T19:55:32Z")
Hello, I am using inputs for in-line MEGANv3.2 from the 2018 EPA modeling platform, including a FERT\_CONUS file to be used with BDSNP. From a previous communication with @willison.jeff , this was generated by the model … --- ## [Issue Running MEGAN3.2 txt2ioapi](https://forum.cmascenter.org/t/issue-running-megan3-2-txt2ioapi/5617)
**Author:** [@yan2024](https://forum.cmascenter.org/u/yan2024)\ **Replies:** 13\ **Last updated:** [July 2, 2025, 12:18pm UTC](https://forum.cmascenter.org/t/issue-running-megan3-2-txt2ioapi/5617 "2025-07-02T12:18:32Z")
Hello Teachers, I am using MEGAN3.2 to generate input files for CMAQ online coupling. I attempted to run the script run.txt2ioapi.csh from the ‘work’ directory, but both the terminal output and the log file were complet… --- ## [ERROR in MEGAN OUTPUT CT3.csv](https://forum.cmascenter.org/t/error-in-megan-output-ct3-csv/5881)
**Author:** [@Sunchanglei](https://forum.cmascenter.org/u/Sunchanglei)\ **Replies:** 2\ **Last updated:** [July 2, 2025, 8:26am UTC](https://forum.cmascenter.org/t/error-in-megan-output-ct3-csv/5881 "2025-07-02T08:26:50Z")
Dear teachers, I used MEGAN32\_prep\_code to generate the CT3.csv, but when I tried to run it in the run.txt2ioapi.v32.csh script, it failed. From the CT3.csv, I found that there were many “100” values present. I think thi… --- ## [MEGAN 3.1 Error : running run.mgn2mech.v31.csh](https://forum.cmascenter.org/t/megan-3-1-error-running-run-mgn2mech-v31-csh/5832)
**Author:** [@summer](https://forum.cmascenter.org/u/summer)\ **Replies:** 0\ **Last updated:** [May 28, 2025, 3:15pm UTC](https://forum.cmascenter.org/t/megan-3-1-error-running-run-mgn2mech-v31-csh/5832 "2025-05-28T15:15:43Z")
Dear Professors, I am encountering some issues while running MEGAN3.1 and would greatly appreciate your assistance. In the ‘run.mgn2mech.v31.csh’ file within the ‘MEGAN31\_Calc\_Code’ module, I set the mechanism to SAPRC… --- ## [MEGAN 2.1 installation errors](https://forum.cmascenter.org/t/megan-2-1-installation-errors/4471)
**Author:** [@SolL](https://forum.cmascenter.org/u/SolL)\ **Replies:** 11\ **Last updated:** [June 22, 2025, 7:35am UTC](https://forum.cmascenter.org/t/megan-2-1-installation-errors/4471 "2025-06-22T07:35:27Z")
Hello there. Im trying to compile and run Megan 2.1 with the pgf90 compiler. First all, I had the IOAPI and netcdf libraries already installed but with ifort. Is it necessary to reinstall them with pgf90? Besides that,… --- ## [./run.met2mgn.v32.csh error](https://forum.cmascenter.org/t/run-met2mgn-v32-csh-error/4851)
**Author:** [@liuhao](https://forum.cmascenter.org/u/liuhao)\ **Replies:** 3\ **Last updated:** [June 3, 2025, 11:48am UTC](https://forum.cmascenter.org/t/run-met2mgn-v32-csh-error/4851 "2025-06-03T11:48:18Z")
Hi everyone, I’m currently running the Megan 3.2 model. My wrfout time step is 6 hours, starting from 2017-06-01\_00:00. When running MCIP, it requires a time later than the start time, so the initial time of the MCIP ou… --- ## [EFMAP difference unit in V2.1 and v3.2](https://forum.cmascenter.org/t/efmap-difference-unit-in-v2-1-and-v3-2/5775)
**Author:** [@amin](https://forum.cmascenter.org/u/amin)\ **Replies:** 1\ **Last updated:** [May 6, 2025, 7:37pm UTC](https://forum.cmascenter.org/t/efmap-difference-unit-in-v2-1-and-v3-2/5775 "2025-05-06T19:37:01Z")
Hi All, I created a EFMAP.ncf file using MEGAN v3.2 and the unit for the pollutants is nanomol/m^2/s in this file. I compare this file with a EFMAP.ncf file which created using MEGAN v2.1 and I see the pollutants don’t … --- ## [EFMAP for different days](https://forum.cmascenter.org/t/efmap-for-different-days/5773)
**Author:** [@amin](https://forum.cmascenter.org/u/amin)\ **Replies:** 1\ **Last updated:** [May 1, 2025, 12:48pm UTC](https://forum.cmascenter.org/t/efmap-for-different-days/5773 "2025-05-01T12:48:42Z")
Hello All, I created the OutputGridEF.csv and EFMAP.ncf files using MEGAN v3.2. Since these files have one emission factor for each gridcell and only one time-step, respectively, I’m just wondering how CMAQ-INLINEMEGAN … --- ## [MEGAN BDSNP and NOAH LSM](https://forum.cmascenter.org/t/megan-bdsnp-and-noah-lsm/5766)
**Author:** [@wxy](https://forum.cmascenter.org/u/wxy)\ **Replies:** 2\ **Last updated:** [April 29, 2025, 4:15am UTC](https://forum.cmascenter.org/t/megan-bdsnp-and-noah-lsm/5766 "2025-04-29T04:15:54Z")
Hello everyone, I am trying to use BDSNP in MEGAN to estimate soil emissions. I noticed that the user instructions state that the BDSNPmust be used with PX LSM. But I only have meteorological data based on the NOAH LSM.… --- ## [PFILE for MEGAN v3.2](https://forum.cmascenter.org/t/pfile-for-megan-v3-2/5765)
**Author:** [@amin](https://forum.cmascenter.org/u/amin)\ **Replies:** 1\ **Last updated:** [April 25, 2025, 1:11pm UTC](https://forum.cmascenter.org/t/pfile-for-megan-v3-2/5765 "2025-04-25T13:11:40Z")
Hello All, I run the met2meg for MEGAN v3.2. It seems that it needs the “PFILE” for running. I just wondering how the PFILE is created or which script or program create this PFILE? Thanks in advance. --- ## [Issue with running run.txt2ioapi.v32.csh](https://forum.cmascenter.org/t/issue-with-running-run-txt2ioapi-v32-csh/5749)
**Author:** [@amin](https://forum.cmascenter.org/u/amin)\ **Replies:** 2\ **Last updated:** [April 18, 2025, 6:04pm UTC](https://forum.cmascenter.org/t/issue-with-running-run-txt2ioapi-v32-csh/5749 "2025-04-18T18:04:12Z")
Hello All, I’m running the run.txt2ioapi.v32.csh script in MEGAN v3.2 with the following run control: setenv RUN\_EFS T setenv RUN\_CANTYP T setenv RUN\_LDF T It successfully changes the EFS. csv and LDF… --- ## [MEGAN v3.2 Preprocessing Run](https://forum.cmascenter.org/t/megan-v3-2-preprocessing-run/5730)
**Author:** [@amin](https://forum.cmascenter.org/u/amin)\ **Replies:** 1\ **Last updated:** [April 12, 2025, 12:28am UTC](https://forum.cmascenter.org/t/megan-v3-2-preprocessing-run/5730 "2025-04-12T00:28:32Z")
I want to run the premegan4cmaq.growthform.inp and other .inp files and in this file we have the following: &windowdefs x0 = 1, y0 = 1, ncolsin = 1000, nrowsin = 1000, I’m just wondering w… --- ## [Wilting points in MEGANv3.2](https://forum.cmascenter.org/t/wilting-points-in-meganv3-2/5722)
**Author:** [@Huazhen](https://forum.cmascenter.org/u/Huazhen)\ **Replies:** 4\ **Last updated:** [April 8, 2025, 8:49pm UTC](https://forum.cmascenter.org/t/wilting-points-in-meganv3-2/5722 "2025-04-08T20:49:14Z")
Hi, The wilting points for different soil types are shown in the Figure (from MEGSEA.EXT). I want to ask how these wilting points were determined. The soil moisture in California in July 2021 (drought period) and Ju… --- ## [MEGAN output unit conversion: from mol/s to mol/s/km2](https://forum.cmascenter.org/t/megan-output-unit-conversion-from-mol-s-to-mol-s-km2/5719)
**Author:** [@Huazhen](https://forum.cmascenter.org/u/Huazhen)\ **Replies:** 3\ **Last updated:** [April 7, 2025, 8:36pm UTC](https://forum.cmascenter.org/t/megan-output-unit-conversion-from-mol-s-to-mol-s-km2/5719 "2025-04-07T20:36:37Z")
Hi, The offline MEGAN output isoprene unit is mol/s. I want to convert the unit (mol/s) to mol/s/km2. The spatial resolution is 4km \* 4km. Can I do the unit conversion by simply dividing the output isoprene by 16? Than… --- ## [How to properly make LAIv files for MEGAN3.2](https://forum.cmascenter.org/t/how-to-properly-make-laiv-files-for-megan3-2/5691)
**Author:** [@wxy](https://forum.cmascenter.org/u/wxy)\ **Replies:** 6\ **Last updated:** [April 6, 2025, 10:38am UTC](https://forum.cmascenter.org/t/how-to-properly-make-laiv-files-for-megan3-2/5691 "2025-04-06T10:38:42Z")
Hello everyone, I am working on making LAIv input files for MEGAN 3.2. I am familiar with LAI but not so much with LAIv and MEGAN. I understand that LAIv is the ratio of LAI to vegetation cover fraction (VCF). My questi… --- ## [Error in run.emproc of megan2.1](https://forum.cmascenter.org/t/error-in-run-emproc-of-megan2-1/5645)
**Author:** [@tting](https://forum.cmascenter.org/u/tting)\ **Replies:** 1\ **Last updated:** [March 31, 2025, 2:58pm UTC](https://forum.cmascenter.org/t/error-in-run-emproc-of-megan2-1/5645 "2025-03-31T14:58:18Z")
Hi everyone! I’m using MEGAN2.1 to calculate biogenic emissions and got errors on the last day of each year (December 31st). Does anyone know what might be causing this? Here is the log: …… Entering CANOPY: 19… --- ## [Leaf Index Area and Plant Funtional Type outside of North America (Megan 2.1)](https://forum.cmascenter.org/t/leaf-index-area-and-plant-funtional-type-outside-of-north-america-megan-2-1/4594)
**Author:** [@SolL](https://forum.cmascenter.org/u/SolL)\ **Replies:** 14\ **Last updated:** [March 31, 2025, 12:19pm UTC](https://forum.cmascenter.org/t/leaf-index-area-and-plant-funtional-type-outside-of-north-america-megan-2-1/4594 "2025-03-31T12:19:41Z")
Hello there. Im trying to run the preprocessor tool for Megan 2.1. It is my understanding that I need to run both the leaf index area and plant functional type pre processors to regrid the input data to my domain of in… --- ## [MEGAN 3.2 Error Compiling](https://forum.cmascenter.org/t/megan-3-2-error-compiling/5648)
**Author:** [@asdfg585](https://forum.cmascenter.org/u/asdfg585)\ **Replies:** 1\ **Last updated:** [March 30, 2025, 8:00pm UTC](https://forum.cmascenter.org/t/megan-3-2-error-compiling/5648 "2025-03-30T20:00:43Z")
Dear friends, I’m new to Megan model, and I’m trying to use the gfortran and also ifort compiler to build the MEGANv3.2.I’m getting error in the installation and I need help.I’m sharing my “makefile”. 1.Computer system… --- ## [Download MEGAN v3.21 Emission Factor Processor python code](https://forum.cmascenter.org/t/download-megan-v3-21-emission-factor-processor-python-code/5621)
**Author:** [@Huazhen](https://forum.cmascenter.org/u/Huazhen)\ **Replies:** 3\ **Last updated:** [March 12, 2025, 3:38pm UTC](https://forum.cmascenter.org/t/download-megan-v3-21-emission-factor-processor-python-code/5621 "2025-03-12T15:38:29Z")
Hi, I try to download the MEGAN v3.21 Emission Factor Processor python code and input files. But I found that the MEGAN\_EFP python code doesn’t exist in the google drive provided by the website UCI BAI - MEGAN32. Could … --- ## [Megan v3.2 TXT2IOAPI time step error](https://forum.cmascenter.org/t/megan-v3-2-txt2ioapi-time-step-error/5566)
**Author:** [@nenghan](https://forum.cmascenter.org/u/nenghan)\ **Replies:** 5\ **Last updated:** [February 4, 2025, 2:28pm UTC](https://forum.cmascenter.org/t/megan-v3-2-txt2ioapi-time-step-error/5566 "2025-02-04T14:28:57Z")
Hi, all, I met a time error as the figure shows when I convert csv to nc, it’s ok for LAI, EF (figure #1) etc. but not for cantype (figure #2), the TFLAG in nc is not right (figure #3) I used IOAP3.1, before run … --- ## [Meganv3.2 txt2ioapi error when run CANTYPE](https://forum.cmascenter.org/t/meganv3-2-txt2ioapi-error-when-run-cantype/5559)
**Author:** [@nenghan](https://forum.cmascenter.org/u/nenghan)\ **Replies:** 0\ **Last updated:** [January 31, 2025, 5:28pm UTC](https://forum.cmascenter.org/t/meganv3-2-txt2ioapi-error-when-run-cantype/5559 "2025-01-31T17:28:23Z")
Hi, all, when I run txt2ioapi to create CANTYPE using the file attached below, but I met the error ‘is not valid’, I understand it’s might because the first line of CT3.csv file, I have try to re-enter the name, but it … --- ## [Input data for pre-processor MEGAN](https://forum.cmascenter.org/t/input-data-for-pre-processor-megan/5549)
**Author:** [@Eli](https://forum.cmascenter.org/u/Eli)\ **Replies:** 1\ **Last updated:** [January 30, 2025, 8:25pm UTC](https://forum.cmascenter.org/t/input-data-for-pre-processor-megan/5549 "2025-01-30T20:25:32Z")
Hi everyone, in this website I find tre sub chapters (‘Geogridded input data’, ‘emission factor processor’ and ‘preprocessor, emission calculator and mechanism mapper’). What are the difference of these? [Next page](https://forum.cmascenter.org/c/megan/56.md?page=1)