Model of Emissions of Gases and Aerosols from Nature (MEGANv3.3)

megan is a model used to estimate biogenic VOCs emissions, it has been developed by Alex Guenther and his group.

Dependencies:

• Fortran GNU compiler
• NetCDF library

⚠ At this moment it only works on UNIX/Linux O.S.

Get MEGAN input data:

In order to run megan you will need meteorological and land data.

Data required:

• WRF output NetCDF file.
• Land, vegetation and soil fields needed to run prep_megan. Global data is freely available from MEGAN GLOBAL DATA.

Build

Go to the src directory:

> cd src/

Edit the Makefile to set the compiler and path to NetCDF lib and include files.

> make

If the compilation is successful, the executable meganv3.3.exe should be created at the ./exe directory.

⚠ Note that the variables must be adjusted to match the appropriate values for your system. Check your nc-config --libdir and nc-config --includedir to fill NetCDF flags on Makefile.

Run

Edit the namelist namelist_megan that contains the following variables:

&megan_nl
   start_date='2019-01-01 18:00:00',  !YYYY-MM-DD HH:MM:SS
   end_date  ='2019-01-02 07:00:00',  !YYYY-MM-DD HH:MM:SS

   met_files='wrfout_d01_<date>_<time>', !Pattern of meteo files paths

   LSM='NOAH',                         ! land surface model (LSM) used in meteo

  mechanism='CB05',                    !'RACM2','CB05',CB6_ae7','CRACMM','SAPRC07',

   static_file='prep_mgn_static.nc',   ! NetCDF file w/ CTF, EFs, LDF & LAND  layers (created by prep_megan)
  dynamic_file='prep_mgn_dynamic.nc',  ! NetCDF file w/ LAI, NDEP & NFERT leyers     (created by prep_megan)

  run_bdsnp  = .false. ,               ! run bdsnp soil model for NO emissions?
  prep_megan = .false.,                ! run prep_megan?
/
&prep_megan_nl
   griddesc='GRIDDESC',                        !GRIDDESC file (describing grid and proj)
   gridname='MERC_TEST',!'LCC_TAN_TEST',       !gridname to use in GRIDDESC file

   eco_glb='input/veg_Ecotypes.nc',            ! global ecotype
   ctf_glb='input/veg_GrowthFormFracions.nc',  ! global canopy type fraction
   lai_glb='input/veg_LAIv.nc',                ! global leaf area index

   clim_glb='input/soil_climate.nc',           ! global arid/nonarid soils
   land_glb='input/soil_landtype.nc',          ! global land type data
   ndep_glb='input/soil_nitro.nc',             ! global N-deposition flux
   fert_glb='input/soil_fert.nc',              ! global N-fertilization flux

   GtEcoEF="db/GtEFbyEcotype.csv",             !Emission factor of each GT grouped by Ecotype
/

⚠ Note that the variables must be adjusted to match the appropriate values for your run.

Then execute megan_v3.3.exe:

> ./megan_v3.3.exe < namelist_megan

Please feel free to contact the developer if you have any issues or suggestions.

---

Planned future improvements:

• Portability.
  • Find an alternative to sys calls for date function.
• Input/Output.
  • Incorporate prep-megan.
  • Reading multiple meteoroligcal files.
  • Support to others meteorological models.
• Science.
  • Calculate one gamma per CANTYPE. Then use the corresponding EF for this gamma.
  • Implement bdsnp.