MERRA-2 implementation details

Required coding changes in GEOS-Chem

As noted in the section above, the similarities between MERRA and GEOS-FP (especially of the vertical grids) means that in most cases we can just treat MERRA in the same way as for GEOS-5. In many areas of the code, the coding changes are straightforward and simply involve an extension of C-preprocessor statements such as:

#if defined( GEOS_5 ) || defined( MERRA )

to

#if defined( GEOS_5 ) || defined( MERRA ) || defined( GEOS_FP ) || defined( MERRA2 )

In other areas of GEOS-Chem the changes are more involved. Below we provide a description of the areas of GEOS-Chem that were modified for MERRA:

Top-level directory

File	Modifications made
Makefile_header.mk	If MET=merra2 or MET=merra-2 (case-insensitive), then activate the MERRA2 C-preprocessor switch i.e. Add -DMERRA2 to the Makefile variable USER_DEFS. If GRID=05x0625 is added, then activate the GRID05x0625 C-preprocessor switch i.e. Add -DGRID05x0625 to the Makefile variable USER_DEFS.

--Bob Y. (talk) 21:25, 11 August 2015 (UTC)

Headers directory

The following modifications for MERRA2 were made in the Headers/ directory:

File	Modifications made
CMN_SIZE_mod.F	Added size parameters for GEOS-FP grids at 4° x 5° 2° x 2.5° and 0.25° x 0.3125° resolution
gigc_input_opt_mod.F90	Add MERRA2_DIR to the OptInput derived type Set Input_Opt%MERRA2_DIR = './' in routine Init_GIGC_Input_Opt
gigc_state_met_mod.F90	Multiple instances: Now use: #if defined( GEOS_FP ) || defined( MERRA ) || defined( MERRA2 )

--Bob Y. (talk) 21:26, 11 August 2015 (UTC)

GeosUtil directory

The following modifications for GEOS-FP were made in the GeosUtil/ directory:

File	Modifications made
bpch2_mod.F	In routine GET_MODELNAME: Add MERRA2_47L and MERRA2 modelnames to the #if block In routine GET_NAME_EXT: Return grid name merra2 for MERRA2 fields In routine GET_NAME_EXT_2D: Now use #if defined( MERRA ) || defined( MERRA2 ) In routine GET_RES_EXT: Return resolution string 05x0625 for 0.5° x 0.625° grids
pressure_mod.F	In routines GET_PEDGE and GET_PEDGE_FULLGRID: Compute PEDGE for MERRA2 in the same way as for GEOS-5, MERRA, and GEOS-FP In routine INIT_PRESSURE: Initialize Ap and Bp for MERRA2 in the same way as for GEOS-5, MERRA, and GEOS-FP
time_mod.F	In routine GET_A1_TIME: Compute the DATE array for MERRA2 the same way as is done for MERRA and GEOS-FP
transfer_mod.F	In several routines: Changed code to #if defined( GEOS_5 ) || defined( MERRA ) || defined( GEOS_FP ) || defined( MERRA2 )

--Bob Y. (talk) 21:40, 11 August 2015 (UTC)

GeosCore directory

The following modifications for GEOS-FP were made in the GeosCore/ directory:

File	Modifications made
calcrate.F	Multiple instances: Now use: #if defined( GEOS_5 ) || defined( MERRA ) || defined( GEOS_FP ) || defined( MERRA2 )
carbon_mod.F	Multiple instances: Now use: #if defined( GEOS_5 ) || defined( MERRA ) || defined( GEOS_FP ) || defined( MERRA2 )
cldice_HbrHOBr_mod.F	Multiple instances: Now use: #if defined( GEOS_5 ) || defined( MERRA ) || defined( GEOS_FP ) || defined( MERRA2 )
convection_mod.F	In routine DO_CONVECTION: Changed code to: #if defined( MERRA ) || defined( GEOS_FP ) || defined( MERRA2 )
dao_mod.F	In routine COPY_I6_FIELDS: Changed code to: #if defined( GEOS_FP ) || defined( MERRA2 ) In routine INTERP: Changed code to: #if defined( GEOS_FP ) || defined( MERRA2 )
depo_mercury_mod.F	In routine ADD_Hg2_SNOWPACK Changed code to: #if defined( MERRA ) || defined( GEOS_FP ) || defined( MERRA2 )
dust_dead_mod.F	In routine DST_MBL: For GEOS-FP, add a new value for parameter FLX_MSS_FDG_FCT. The scale factor ensures that we get the same dust totals (w/in roundoff error) as for GEOS-5.
fast_jx_mod.F	In routine FAST_JX: Do cloud overlapping for GEOS-FP in the same way as for GEOS-5 and MERRA. Now use: #if defined( GEOS_5 ) || defined( MERRA ) || defined( GEOS_FP ) || defined( MERRA2 )
gamap_mod.F	In routine INIT_TRACERINFO: Changed code to: #elif defined( GEOS_5 ) || defined( MERRA ) || defined( GEOS_FP )
geosfp_read_mod.F90	Added this module w/ routines to read GEOS-FP met data (in netCDF format)
global_ch4_mod.F	In routines WETLAND_EMIS and READ_COPROD: Now use: #if defined( GEOS_5 ) || defined( MERRA ) || defined( GEOS_FP )
input_mod.F	In routine READ_SIMULATION_MENU: Read value for GEOS_FP_DIR from input.geos file and save into Input_Opt Set LUNZIP=.FALSE. for GEOS-FP met In routine READ_CONVECTION_MENU: Change #if statement to allow non-local PBL mixing for GEOS-FP met data In routine READ_EMISSIONS_MENU: Turn off LMEGANMONO when LMEGAN is turned off In routine VALIDATE_DIRECTORIES: Error check GEOS_FP_DIR for start & end date
land_mercury_mod.F	In routines LAND_MERCURY_FLUX: Changed code to: #if defined( MERRA ) || defined( GEOS_FP ) In routines SOILEMIS: Changed code to: #if defined( MERRA ) || defined( GEOS_FP ) Extend #if statement for variable SOIL_EMIS_FAC to get the code to compile w/o error. (NOTE: Team Hg: you will have to submit a proper value for this later.
lightning_nox_mod.F	In routine LIGHTNING: Eliminate the shallow-cloud inhibititon trap for GEOS-FP, as we already do for GEOS-5 and MERRA In routine GET_OTD_LIS_SCALE: Now use updated values for ANN_AVG_FLASHRATE computed by Lee Murray (2013-11-07).
main.F	Rewrote USE statements for clarity Added calls to routines from geosfp_read_mod.F Split off the code that reads met fields into internal subroutines READ_INITIAL_MET_FIELDS and READ_MET_FIELDS, for clarity. Renamed NN to NNN to avoid name confusion
mercury_mod.F	In routine CHEM_Hg0_Hg2: In the block that computes LWC, changed code to: #if defined( GEOS_5 ) || defined( MERRA ) || defined( GEOS_FP ) In the block that computes Hg0 exchange, changed code to: #if defined( MERRA ) || defined( GEOS_FP )
ocean_mercury_mod.F	Multiple instances: Now use: #if defined( MERRA ) || defined( GEOS_FP )
planeflight_mod.F	In routine PLANEFLIGHT Now use: #if defined( MERRA ) || defined( GEOS_FP )
strat_chem_mod.F90	Multiple instances: Now use: #if defined( GEOS_5 ) || defined( MERRA ) || defined( GEOS_FP )
sulfate_mod.F	Multiple instances: Now use: #if defined( GEOS_5 ) || defined( MERRA ) || defined( GEOS_FP )
tagged_ox_mod.F	In routine GET_REGIONAL_POX: Now use: #if defined( GEOS_5 ) || defined( MERRA ) || defined( GEOS_FP ) || defined( MERRA2 )
tpcore_bc_mod.F:	Multiple instances: Now use: #if defined( GEOS_5 ) || defined( MERRA ) || defined( GEOS_FP )
vdiff_mod.F90	In routine VDIFFDR: Changed code to: #if defined( MERRA ) || defined( GEOS_FP )
wetscav_mod.F	In routines DO_WETDEP, DO_WASHOUT_ONLY Changed code to: #if defined( MERRA ) || defined( GEOS_FP ) In routine MAKE_QQ: Add #if block for GEOS-FP met Refer to PFILSAN(I,J,L+1) and PFLLSAN(I,J,L+1), since these fields are defined on level edges In routine RAINOUT: Changed code to: #if defined( GEOS_5 ) || defined( MERRA ) || defined( GEOS_FP )

--Bob Y. (talk) 22:13, 11 August 2015 (UTC)