List of MERRA-2 met fields

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MERRA-2 is a new NASA/GMAO reanalysis product. It has a horizontal resolution of 0.5° lat x 0.625° lon x 72 vertical levels. The horizontal resolution is 2x coarser than the GMAO "forward processing" product (which we refer to as GEOS-FP). But MERRA-2 uses the identical vertical grid as the GEOS-5, MERRA, and the "GEOS-FP" data products used by GEOS-Chem.

NOTE: GEOS-Chem only uses a subset of the entire MERRA-2 data archive. On this page we list the MERRA-2 met fields that we archive for use with GEOS-Chem.

Constant fields

Overview:

Quantities archived in this file type:	Time-invariant fields These are mostly parameters pertaining to the horizontal grid
File naming convention:	`MERRA2.20150101.CN.05x0625.CH.nc` (Native resolution nested CH grid) `MERRA2.20150101.CN.05x0625.EU.nc` (Native resolution nested EU grid) `MERRA2.20150101.CN.05x0625.NA.nc` (Native resolution nested NA grid) `MERRA2.20150101.CN.05x0625.NA.nc` (Native resolution nested SE grid) `MERRA2.20150101.CN.2x25.nc` (2° x 2.5° global grid) `MERRA2.20150101.CN.4x5.nc` (4° x 5° global grid)
Timestamps:	For convenience, we have assigned these data timestamp of `2015/01/01 00:00 UTC`

List of MERRA-2 data fields in this file type:

Field	Units	Collection	Standard name	Notes	Where used in GEOS-Chem?
FRLAKE	1	const_2d_asm_Nx	fraction_of_lake		CH4 simulation, diagnostics
FRLAND	1	const_2d_asm_Nx	fraction_of_land		Chemistry Hg simulation CH4 simulation PBL mixing
FRLANDIC(E)	1	const_2d_asm_Nx	fraction_of_land_ice	The original name in the GEOS-FP raw data files is FRLANDICE. We shorten this to FRLANDIC for GEOS-Chem. GEOS-Chem requires 8-character met field names.	Hg simulation CH4 simulation PBL mixing
FROCEAN	1	const_2d_asm_Nx	fraction_of_ocean		Chemistry Hg simulation CH4 simulation Emissions
PHIS	m² s^-2	const_2d_asm_Nx	surface_geopotential_height		Kept for diagnostics

--Bob Y. (talk) 18:19, 3 August 2015 (UTC)

A1 fields

Overview:

Quantities archived in this file type:	Various surface fields
File naming convention:	`MERRA2.YYYYMMDD.A1.05x0625.CH.nc` (Native resolution nested CH grid) `MERRA2.YYYYMMDD.A1.05x0625.EU.nc` (Native resolution nested EU grid) `MERRA2.YYYYMMDD.A1.05x0625.NA.nc` (Native resolution nested NA grid) `MERRA2.YYYYMMDD.A1.025x03125.SE.nc` (Native resolution nested SE grid) `MERRA2.YYYYMMDD.A1.2x25.nc` (2° x 2.5° global grid) `MERRA2.YYYYMMDD.A1.4x5.nc` (4° x 5° global grid)
Timestamps:	00:30, 01:30, 02:30, 3:30, 4:30, 5:30 ... 23:30 GMT These represent the center of the 1-hour averaging period

List of MERRA-2 data fields in this file type:

Field	Units	Collection	Standard name	Notes	Where used in GEOS-Chem?
ALBEDO	1	tavg1_2d_rad_Nx	surface_albedo		Dry deposition Diagnostics
CLDTOT	1	tavg1_2d_rad_Nx	total_cloud_area_fraction	For all intents and purposes, CLDTOT = the column sum of CLOUD, but at 1-hour resolution.	Photolysis Diagnostics
EFLUX	W m^-2	tavg1_2d_flx_Nx	total_latent_energy_flux		Kept for diagnostics
EVAP	kg m^-2 s^-2	tavg1_2d_flx_Nx	evaporation_from_turbulence		Kept for diagnostics
FRSEAICE	1	tavg1_2d_flx_Nx	ice_covered_fraction_of_tile	We bin FRSEAICE to create the SEAICE** fields listed below.	Hg simulation
FRSNO	1	tavg1_2d_lnd_Nx	fractional_area_of_land_snowcover		PBL mixing Hg simulation
GRN	1	tavg1_2d_lnd_Nx	greenness_fraction		Kept for diagnostics
GWETROOT	1	tavg1_2d_lnd_Nx	root_zone_soil_wetness		Kept for diagnostics
GWETTOP	1	tavg1_2d_lnd_Nx	surface_soil_wetness		CH4 simulation Dust mobilization
HFLUX	W m^-2	tavg1_2d_flx_Nx	sensible_heat_flux_from_turbulence		Dry deposition
LAI	m² m^-2	tavg1_2d_lnd_Nx	leaf_area_index	NOTE: GEOS-Chem uses MODIS LAI instead of the GEOS-FP LAI..	Kept for diagnostics
LWGNT	W m^-2	tavg1_2d_rad_Nx	surface_net_downward_longwave_flux		Kept for diagnostics
LWI	1	-	land_water_ice_flags	We derive LWI from the FRSEAICE, FROCEAN, and FRLAND fields. GEOS-Chem needs LWI for backwards compatibility.	To determine the overall surface type in a grid box
LWTUP	W m^-2	tavg1_2d_rad_Nx	upwelling_longwave_flux_at_toa		Kept for diagnostics
PARDF	W m^-2	tavg1_2d_lnd_Nx	surface_downwelling_par_diffuse_flux	The name of this data field in the raw data file is "PARDFLAND".	Biogenic emissions
PARDR	W m^-2	tavg1_2d_lnd_Nx	surface_downwelling_par_beam_flux	The name of this data field in the raw data file is "PARDRLAND".	Biogenic emissions
PBLH	m	tavg1_2d_flx_Nx	planetary_boundary_layer_height		PBL mixing
PRECANV	kg m^-2 s^-1	tavg1_2d_flx_Nx	anvil_precipitation		Kept for diagnostics
PRECCON	kg m^-2 s^-1	tavg1_2d_flx_Nx	convective_precipitation		Soil NOx emissions Wet deposition
PRECLSC	kg m^-2 s^-1	tavg1_2d_flx_Nx	nonanvil_large_scale_precipitation		Kept for diagnostics
PRECSNO	kg m^-2 s^-1	tavg1_2d_flx_Nx	snowfall		Kept for diagnostics
PRECTOT	kg m^-2 s^-1	tavg1_2d_flx_Nx	total_precipitation		Soil NOx emissions Wet deposition
QV2M	kg kg^-1	tavg1_2d_slv_Nx	2-meter_specific_humidity		Kept for diagnostics
Q850	kg kg^-1	tavg1_2d_slv_Nx	specific_humidity_at_850_hPa		Dust mobilization
SEAICE00	1	-	sea_area_ice_fraction_0-10%	We create this by binning FRSEAICE.	Arctic simulations Diagnostics
SEAICE10	1	-	sea_area_ice_fraction_10-20%	We create this by binning FRSEAICE.	Arctic simulations Planeflight diagnostic
SEAICE20	1	-	sea_area_ice_fraction_20-30%	We create this by binning FRSEAICE.	Arctic simulations Planeflight diagnostic
SEAICE30	1	-	sea_area_ice_fraction_30-40%	We create this by binning FRSEAICE.	Arctic simulations Planeflight diagnostic
SEAICE40	1	-	sea_area_ice_fraction_40-50%	We create this by binning FRSEAICE.	Arctic simulations Planeflight diagnostic
SEAICE50	1	-	sea_area_ice_fraction_50-60%	We create this by binning FRSEAICE.	Arctic simulations Planeflight diagnostic
SEAICE60	1	-	sea_area_ice_fraction_60-70%	We create this by binning FRSEAICE.	Arctic simulations Planeflight diagnostic
SEAICE70	1	-	sea_area_ice_fraction_70-80%	We create this by binning FRSEAICE.	Arctic simulations Planeflight diagnostic
SEAICE80	1	-	sea_area_ice_fraction_80-90%	We create this by binning FRSEAICE.	Arctic simulations Planeflight diagnostic
SEAICE90	1	-	sea_area_ice_fraction_90-100%	We create this by binning FRSEAICE.	Arctic simulations Planeflight diagnostic
SLP	Pa	tavg1_2d_slv_Nx	sea_level_pressure	We keep the original units of Pa. We convert to hPa when reading into GEOS-Chem.	Kept for diagnostics
SNODP	m	tavg1_2d_lnd_Nx	snow_depth		Kept for diagnostics
SNOMAS	kg m^-2	tavg1_2d_lnd_Nx	Total_snow_storage_land		Dust mobilization Hg simulations Dry deposition
SWGDN	W m^-2	tavg1_2d_rad_Nx	surface_incoming_shortwave_flux	GEOS-Chem carries this as `State_Met%RADSWG`	Soil NOx emissions Hg simulations Dry deposition
TO3	Dobsons	tavg1_2d_slv_Nx	total_column_ozone		Used as input to photolysis
TROPPT	hPa	tavg1_2d_slv_Nx	tropopause_pressure_based_on_thermal_estimate	Original units of TROPPT are Pa. We convert Pa -> hPa because GEOS-Chem expects hPa.	Used to determine tropopause height
TS	K	tavg1_2d_slv_Nx	surface_skin_temperature	GEOS-Chem carries this as `State_Met%TSKIN`	CH4 simulation Hg simulation Sea salt emissions
T2M	K	tavg1_2d_slv_Nx	2-meter_air_temperature	GEOS-Chem carries this as `State_Met%TS` GEOS-Chem uses T2M as a proxy for surface air temp.	Many locations
T10M	K	tavg1_2d_slv_Nx	10-meter_air_temperature		Dust mobilization
U10M	m s^-1	tavg1_2d_slv_Nx	10-meter_eastward_wind		Dry deposition Dust mobilization Emissions Sea salt aerosols Hg simulations
USTAR	m s^-1	tavg1_2d_flx_Nx	surface_velocity_scale		Dry deposition
V10M	m s^-1	tavg1_2d_slv_Nx	10-meter_northward_wind		Dry deposition Dust mobilization Emissions Sea salt aerosols Hg simulations
Z0M	m	tavg1_2d_flx_Nx	surface_roughness		Dry deposition

--Bob Y. (talk) 16:21, 3 August 2015 (UTC)

A3cld fields

Overview:

Quantities archived in this file type:	Cloud parameters Data are 3-dimensional, stored at the midpoint of each vertical level
File naming convention:	`MERRA2.YYYYMMDD.A3cld.05x0625.CH.nc` (Native resolution, nested CH grid) `MERRA2.YYYYMMDD.A3cld.05x0625.EU.nc` (Native resolution, nested EU grid) `MERRA2.YYYYMMDD.A3cld.05x0625.NA.nc` (Native resolution, nested NA grid) `MERRA2.YYYYMMDD.A3cld.05x0625.SE.nc` (Native resolution, nested SE grid) `MERRA2.YYYYMMDD.A3cld.2x25.nc` (2° x 2.5° global grid) `MERRA2.YYYYMMDD.A3cld.4x5.nc` (4° x 5° global grid)
Timestamps:	01:30, 04:30, 07:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT Timestamps represent the center of the 3-hour averaging period.

List of MERRA-2 data fields in this file type:

Field	Units	Collection	Standard name	Notes	Where used in GEOS-Chem?
CLOUD	1	tavg3_3d_cld_Nv	cloud_fraction_for_radiation	We regrid CLOUD w/ Hongyu Liu's algorithm.	Photolysis Chemistry
OPTDEPTH	1	none	in_cloud_optical_thickness	We create OPTDEPTH = TAUCLI + TAUCLW. We regrid OPTDEPTH w/ Hongyu Liu's algorithm.	Photolysis Chemistry
QI	kg kg^-1	none	mass_fraction_of_cloud_ice_water		Chemistry Aerosol microphysics
QL	kg kg^-1	tavg3_3d_cld_Nv	mass_fration_of_cloud_liquid_water		Chemistry Aerosol microphysics
TAUCLI	1	tavg3_3d_cld_Nv	in_cloud_optical_thickness_for_ice_clouds	We use TAUCLI to create OPTDEPTH. We regrid TAUCLI w/ Hongyu Liu's algorithm.	Kept for diagnostics
TAUCLW	1	tavg3_3d_cld_Nv	in_cloud_optical_thickness_for_liquid_clouds	We use TAUCLW to create OPTDEPTH. We regrid TAUCLW w/ Hongyu Liu's algorithm	Kept for diagnostics

--Bob Y. (talk) 17:32, 3 August 2015 (UTC)

A3dyn fields

Overview:

Quantities archived in this file type:	Dynamical fields (e.g. winds, relative humidity, detrainment fluxes) Data are 3-dimensional, stored at the midpoint of each vertical level
File naming convention:	`MERRA2.YYYYMMDD.A3dyn.05x0625.CH.nc` (Native resolution, nested CH grid) `MERRA2.YYYYMMDD.A3dyn.05x0625.EU.nc` (Native resolution, nested EU grid) `MERRA2.YYYYMMDD.A3dyn.05x0625.NA.nc` (Native resolution, nested NA grid) `MERRA2.YYYYMMDD.A3dyn.05x0625.SE.nc` (Native resolution, nested SE grid) `MERRA2.YYYYMMDD.A3dyn.2x25.nc` (2° x 2.5° global grid) `MERRA2.YYYYMMDD.A3dyn.4x5.nc` (4° x 5° global grid)
Timestamps:	01:30, 04:30, 07:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT Timestamps represent the center of the 3-hour averaging period.

List of MERRA-2 data fields in this file type:

Field	Units	Collection	Standard name	Notes	Where used in GEOS-Chem?
DTRAIN	kg m^-2 s^-1	tavg3_3d_cld_Nv	detraining_mass_flux		Cloud convection
OMEGA	Pa s^-1	tavg3_3d_asm_Nv	vertical_pressure_velocity		Kept for diagnostics
RH	1	tavg3_3d_cld_Nv	relative_humidity_after_moist	GMAO computes RH as follows: T > 273.16 K: w/r/t liquid T < 253.16 K: w/r/t ice 253.16 K <= T <= 273.16K: weighted avg w/r/t both liquid and ice	Chemistry Wet deposition Aerosol therm. equilib. Aerosol microphysics
U	m s^-1	tavg3_3d_asm_Nv	eastward_wind		Advection
V	m s^-1	tavg3_3d_asm_Nv	northward_wind		Advection

--Bob Y. (talk) 17:36, 3 August 2015 (UTC)

A3mstC fields

Overview:

Quantities archived in this file type:	Precipitation and sublimation fields Data are 3-dimensional, stored at the midpoint of each vertical level
File naming convention:	`MERRA2.YYYYMMDD.A3mstC.05x0625.CH.nc` (Native resolution, nested CH grid) `MERRA2.YYYYMMDD.A3mstC.05x0625.EU.nc` (Native resolution, nested EU grid) `MERRA2.YYYYMMDD.A3mstC.05x0625.NA.nc` (Native resolution, nested NA grid) `MERRA2.YYYYMMDD.A3mstC.05x0625.SE.nc` (Native resolution, nested SE grid) `MERRA2.YYYYMMDD.A3mstC.2x25.nc` (2° x 2.5° global grid) `MERRA2.YYYYMMDD.A3mstC.4x5.nc` (4° x 5° global grid)
Timestamps:	01:30, 04:30, 07:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT Timestamps represent the center of the 3-hour averaging period.

List of MERRA-2 data fields in this file type:

Field	Units	Collection	Standard name	Notes	Where used in GEOS-Chem?
DQRCU	kg kg^-1 s^-1	tavg3_3d_mst_Nv	convective_rainwater_source		Conv. updraft scavenging
DQRLSAN	kg kg^-1 s^-1	tavg3_3d_mst_Nv	large_scale_rainwater_source		Wet deposition
REEVAPCN	kg kg^-1 s^-1	tavg3_3d_mst_Nv	evap_subl_of_convective_precipitation		Conv. updraft scavenging
REEVAPLS(AN)	kg kg^-1 s^-1	tavg3_3d_mst_Nv	evap_subl_of_non_convective_precipitation	In the GEOS-FP raw data files, this field is named REEVAPLSAN. In the files created for GEOS-Chem, we change the field name to REEVAPLS. GEOS-Chem requires 8-character met field names for backwards compatibility.	Wet deposition

--Bob Y. (talk) 17:46, 3 August 2015 (UTC)

A3mstE fields

Overview:

Quantities archived in this file type:	Precipitation and convection fields Data are 3-dimensional, stored at the edges of each vertical level
File naming convention:	`MERRA2.YYYYMMDD.A3mstE.05x0625.CH.nc` (Native resolution, nested CH grid) `MERRA2.YYYYMMDD.A3mstE.05x0625.EU.nc` (Native resolution, nested EU grid) `MERRA2.YYYYMMDD.A3mstE.05x0625.NA.nc` (Native resolution, nested NA grid) `MERRA2.YYYYMMDD.A3mstE.05x0625.SE.nc` (Native resolution, nested SE grid) `MERRA2.YYYYMMDD.A3mstE.2x25.nc` (2° x 2.5° global grid) `MERRA2.YYYYMMDD.A3mstE.4x5.nc` (4° x 5° global grid)
Timestamps:	01:30, 04:30, 07:30, 10:30, 13:30, 16:30, 19:30, 22:30 GMT Timestamps represent the center of the 3-hour averaging period.

List of MERRA-2 data fields in this file type:

Field	Units	Collection	Description	Notes	Where used in GEOS-Chem?
CMFMC	kg m^-2 s^-1	tavg3_3d_mst_Ne	Upward moist convective mass flux		Cloud convection
PFICU	kg m^-2 s^-1	tavg3_3d_mst_Ne	3d flux of ice convective precipitation		Conv. updraft scavenging
PFILSAN	kg m^-2 s^-1	tavg3_3d_mst_Ne	3d flux of ice non-convective precipitation		Wet deposition
PFLCU	kg m^-2 s^-1	tavg3_3d_mst_Ne	3d flux of liquid convective precipitation		Conv. updraft scavenging
PFLLSAN	kg m^-2 s^-1	tavg3_3d_mst_Ne	3d flux of liquid non-convective precipitation		Wet deposition

--Bob Y. (talk) 18:52, 3 August 2015 (UTC)

I3 fields

Overview:

Quantities archived in this file type:	Pressure, temperature, humidity Data are 3-dimensional, stored at the midpoint of each vertical level
File naming convention:	`MERRA2.YYYYMMDD.I3.05x0625.CH.nc` (Native resolution, nested China grid) `MERRA2.YYYYMMDD.I3.05x0625.EU.nc` (Native resolution, nested Europe grid) `MERRA2.YYYYMMDD.I3.05x0625.NA.nc` (Native resolution, nested North America grid) `MERRA2.YYYYMMDD.I3.05x0625.SE.nc` (Native resolution, nested SE Asia grid) `MERRA2.YYYYMMDD.I3.2x25.nc` (2° x 2.5° global grid) `MERRA2.YYYYMMDD.I3.4x5.nc` (4° x 5° global grid)
Timestamps:	00:00, 03:00, 06:00, 09:00, 12:00, 15:00, 18:00, 21:00 GMT Timestamps represent instantaneous ("snapshot") values every 3 hours.

List of MERRA-2 data fields in this file type:

Field	Units	Collection	Standard name	Notes	Where used in GEOS-Chem?
PS	hPa	inst3_3d_asm_Nv	surface_pressure	We keep the original units of Pa We convert Pa -> hPa when reading the PS field in GEOS-Chem.	Advection Many other locations
PV	K m² kg^-1 s^-1	inst3_3d_asm_Nv	ertels_potential_vorticity	This field is labeled EPV in the GEOS-FP raw data files. GEOS-Chem renames this to "PV" for backwards compatibility with older met products.	Kept for diagnostics
QV	kg kg^-1	inst3_3d_asm_Nv	specific_humidity	In GEOS-Chem: QV at time t is converted to g/kg and saved into `State_Met%SPHU1`; QV at time t+3hr is converted to g/kg and saved into `State_Met%SPHU2`; QV is then interpolated to the current time.	Chemistry Wet deposition PBL mixing
T	K	inst3_3d_asm_Nv	air_temperature	In GEOS-Chem: T @ time t is saved into `State_Met%TMPU1`; T @ time t+3h is saved into `State_Met%TMPU2`; T is then interpolated to the current time.	Many locations

--Bob Y. (talk) 18:56, 3 August 2015 (UTC)

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