Please visit our separate MEGAN biogenic emissions wiki page for the latest information about the implementation of MEGAN in GEOS-Chem.
Retirement of obsolete GEIA biogenic emissions
This update was tested in the 1-month benchmark simulation v9-01-03b and approved on 14 Dec 2011.
Dylan Millet wrote:
- With [Emily Fischer's acetone update], we can now get rid of the geia-related routines:
- Affected routines:
- emissdr.f, carbon_mod.f, tagged_co_mod.f: these just need to have the geia options removed; the megan option is implemented already
- h2_hd_mod.f: needs to be converted from geia to megan for isoprene and monoterpenes.
- Also, I think you can get rid of both CMN_ISOP and CMN_MONOT since the variables they declare are no longer used outside of the routines that you're eliminating. My copy of Emily's updated acetone_mod.f still has a reference to CMN_MONOT, but that's just a leftover, the corresponding array (BASEMONOT) is not actually used.
--Melissa Payer 10:51, 15 December 2011 (EST)
Clarification about isoprene from grasslands
NOTE: This functionality has been removed in GEOS-Chem v9-01-03 and higher versions.
Prasad Kasibhatla wrote:
- In emissdr.f, there are the following 2 lines:
! Isoprene emissions from grasslands (use GEIA always) GRASS = EMISOP_GRASS(I, J,IJLOOP, SUNCOS, TMMP, XNUMOL_C)
- But it looks like further down when emissions of isoprene are saved into an array, the value stored in GRASS is not used:
IF ( IDTISOP /= 0 ) THEN ! NOTE: Don't save into EMISRR for the tagged CO ! simulation (jaf, mak, bmy, 2/14/08) IF ( NO_TAGCO ) THEN EMISRR(I,J,IDEISOP) = EMISRR(I,J,IDEISOP) + & ( EMIS / DTSRCE ) ENDIF ENDIF
- I am a bit confused as to what the grassland isoprene emissions are in relation to non--grassland emissions.
May Fu replied:
- For GEIA, emisop.f calculates the total isoprene emission, including those from grassland. emisop_grass.f calculates the isoprene emission ONLY from grassland and stores it into variable GRASS. You can see this in emisop_grass.f, where the grassland grids are picked out, and then emission factors for grassland is used to calculate the emission. The reason we need to call emisop_grass.f is because the grassland acetone emission is scaled from the grassland isoprene emission.
- In MEGAN, routine GET_EMISOP_MEGAN in megan_mod.f calculates the total isoprene emission. But because the MEGAN emission factors were given as a gridded map, not as a function as land types, there is no easy way to determine the emission from grassland. So we use the GEIA isoprene emission for grassland to calculate acetone emission ONLY, regardless of whether you choose GEIA or MEGAN for isoprene itself.
- In short, the call to function emisop_grass.f indeed should NOT be counted as additional isoprene source.
--Bob Y. 10:49, 16 December 2011 (EST)