GEOS–CHEM v6–02–05 User's Guide
Contact: Bob Yantosca (bmy@io.harvard.edu)

Appendix 4: GEOS–CHEM Meteorological Fields

A4.1 GEOS–1 fields used by GEOS–CHEM
Field Type Dimension Quantity Units
ALBD I-6 2D Surface albedo unitless
LWI I-6 2D Land-water-ice flags unitless
PHIS I-6 2D Surface geopotential heights m2 / s2
PS I-6 2D Surface pressure mb
SPHU I-6 3D Specific humidity g H2O / kg air
TMPU I-6 3D Temperature K
UWND I-6 3D Zonal wind m / s
VWND I-6 3D Meridional wind m / s
CLDMAS A-6 3D Cloud mass flux kg / m2 / 600s
CLMOSW A-6 3D Shortwave maximum overlap cloud fraction Unitless
CLROSW A-6 3D Shortwave random overlap cloud fraction unitless
DTRAIN A-6 3D Cloud detrainment kg / m2 / 600s
MOISTQ A-6 3D Tendency in SPHU field g H2O / kg air / day
CLDFRC A-3 2D Column cloud fraction at ground unitless
HFLUX A-3 2D Sensible heat flux W/m2
PBL A-3 2D Planetary boundary layer depth mb
PREACC A-3 2D Total precipitation at ground mm H2O / day
PRECON A-3 2D Convective precipitation at ground mm H2O / day
RADSWG A-3 2D Shortwave (solar) radiation reaching the ground W / m2
TS A-3 2D Surface air temperature K
U10M A-3 2D UWND at 10 m altitude m / s
USTAR A-3 2D Friction velocity m / s
V10M A-3 2D VWND at 10 m altitude m / s
Z0 A-3 2D Roughness height m

NOTES for GEOS–1 fields:

  1. I-6 fields contain instantaneous ("snapshot") data, at 00, 06, 12, and 18 GMT. GEOS–CHEM linearly interpolates these to intermediate times.

  2. A-6 fields contain 6-hour average data, centered at 00, 06, 12, and 18 GMT. For example, an A-6 data field at 06 GMT is an average between 03 GMT and 09 GMT.

  3. A-3 fields contain 3-hour average data, ended at 00, 03, 06, 09, 12, 15, 18, and 21 GMT. For example, an A-3 data field at 03 GMT is an average from 00 GMT to 03 GMT.

  4. The PHIS field (surface geopotential heights) is temporally invariant, so we only use data for January 1, 1994. Also, the PHIS field is only needed by the full chemistry simulation with SMVGEAR.

  5. Cloud optical depth is computed as a function of CLMOSW, CLROSW, and temperature.

A4.2 GEOS–STRAT fields used by GEOS–CHEM
Field Type Dimension Quantity Units
ALBD I-6 2D Surface albedo unitless
LWI I-6 2D Land-water-ice flags unitless
PHIS I-6 2D Surface geopotential heights m2 / s2
PS I-6 2D Surface pressure mb
SPHU I-6 3D Specific humidity g H2O / kg air
TMPU I-6 3D Temperature K
UWND I-6 3D Zonal wind m / s
VWND I-6 3D Meridional wind m / s
CLDMAS A-6 3D Cloud mass flux kg / m2 /600s
CLMOSW A-6 3D Shortwave maximum overlap cloud fraction Unitless
CLROSW A-6 3D Shortwave random overlap cloud fraction unitless
DTRAIN A-6 3D Cloud detrainment kg / m2 / 600s
MOISTQ A-6 3D Tendency in SPHU field g H2O / kg air / day
HFLUX A-3 2D Sensible heat flux W/m2
PBL A-3 2D Planetary boundary layer depth mb
PREACC A-3 2D Total precipitation at ground mm H2O / day
PRECON A-3 2D Convective precipitation at ground mm H2O / day
RADSWG A-3 2D Shortwave (solar) radiation reaching the ground W / m2
TS A-3 2D Surface air temperature K
U10M A-3 2D UWND at 10 m altitude m / s
USTAR A-3 2D Friction velocity m / s
V10M A-3 2D VWND at 10 m altitude m / s
Z0 A-3 2D Roughness height m

NOTES for GEOS–STRAT fields:

  1. I-6, A-6, and A-3 designations are the same as for the GEOS–1 fields listed above.

  2. The A-3 CLDFRC field was not archived in GEOS–STRAT. This field is computed online from the A-6 CLMOSW and CLROSW fields.

  3. GEOS–STRAT A-3 fields were originally archived at 6 hour temporal resolution. These were interpolated to 3 hour temporal resolution here at Harvard, in order to be consistent with the GEOS–1 fields.

  4. The A-3 HFLUX (Sensible Heat Flux) field was not archived in GEOS–STRAT from December 1, 1995 to February 12, 1997. For this time period, use GEOS–1 HFLUX fields from 1994.

  5. The A-3 U10M and V10M( winds at 10 m altitude) fields were not archived in GEOS–STRAT from December 1, 1995 to February 12, 1997. For this time period, we interpolate UWND and VWND to 10 meters altitude in the code, using the log law.

  6. Cloud optical depth is computed as a function of CLMOSW, CLROSW, and temperature, just as in GEOS–1.

A4.3 GEOS–3 fields used by GEOS–CHEM
Field Type Dimension Quantity Units
ALBD I-6 2D Surface albedo unitless
LWI I-6 2D Land-water-ice flags unitless
PHIS I-6 2D Surface geopotential heights m2 / s2
PS I-6 2D Surface pressure mb
SLP I-6 2D Sea level pressure mb
TROPP I-6 2D Tropospheric top pressure mb
RH I-6 3D Relative humidity %
SPHU I-6 3D Specific humidity g H2O / kg air
TKE I-6 3D Turbulent kinetic energy m2 / s2
TMPU I-6 3D Temperature K
UWND I-6 3D Zonal wind m / s
VWND I-6 3D Meridional wind m / s
CLDMAS A-6 3D Cloud mass flux kg / m2 / 600s
CLDTOT A-6 3D 3D cloud fraction (conv + large scale) unitless
DTRAIN A-6 3D Cloud detrainment kg / m2 / 600s
KH A-6 3D Eddy diffusion coefficient unitless
MOISTQ A-6 3D Tendency in SPHU Field g H2O / kg air / day
TAUCLD A-6 3D In-cloud optical depth unitless
OPTDEPTH A-6 3D Grid box optical depth unitless
CLDFRC A-3 2D Column cloud fraction at ground unitless
HFLUX A-3 2D Sensible heat flux W / m2
PBL A-3 2D Planetary boundary layer depth mb
PREACC A-3 2D Total precipitation at ground mm H2O / day
PRECON A-3 2D Convective precipitation at ground mm H2O / day
RADSWG A-3 2D Shortwave (solar) radiation reaching the ground W / m2
TS A-3 2D Surface temperature K
U10M A-3 2D UWND at 10 m altitude m / s
USTAR A-3 2D Friction velocity m / s
V10M A-3 2D VWND at 10 m altitude m / s
Z0 A-3 2D Roughness height m

NOTES for GEOS–3 fields:

  1. I-6, A-6, and A-3 designations are the same as for the GEOS–1 fields listed above.

  2. The following fields are only contained in the 1998 GEOS–3 dataset provided to us from Arlindo da Silva: RH, TKE, KH. These fields are also currently ignored by GEOS–CHEM, but may be used at a later date.

  3. The following GEOS–3 fields are available only for the years 2000 and 2001: SLP, TROPP.

  4. The GEOS–3 ALBD field for 2000 and 2001 is an average of the direct-beam visible albedo (ALBVISDR) and the diffuse-beam visible albedo (ALBVISDF). This results in a visible albedo field comparable to that in GEOS–1 or GEOS–STRAT. NOTE: Visible albedo is not used for photolysis code; we use UV albedoes from observed TOMS data.

  5. The GEOS–3 CLDTOT field now supersedes the GEOS–1/GEOS–STRAT GEOS–STRAT CLMOSW and CLROSW fields. CLDTOT is the total cloud fraction of both convective and large-scale clouds.

  6. For 2000 and 2001 data, GEOS–3 optical depths are stored in the OPTDEPTH field. This field has been interpolated from pressure coordinates to sigma coordinates, and is the total optical depth in a grid box. TAUCLD is just the in-cloud optical depth.

  7. For 1998 data, GEOS–3 optical depths need to be computed as the product of TAUCLD and CLDTOT. This will produce grid box optical depths similar to the OPTDEPTH field for data from 2000 and 2001, as described above.

  8. For 2000 and 2001 GEOS–3 fields, the surface temperature is not taken from the TGROUND met field, since TGROUND is the temperature of the ground and not of the air. The surface temperature for these years has been taken from the first level of the 3-D temperature field TMPU. This correction has not yet been applied to the data set from Arlindo da Silva for 1998.

A4.4 GEOS–4 fields used by GEOS–CHEM
Field Type Dimension Quantity Units
LWI I-6 2D Land-water-ice flags unitless
PHIS I-6 2D Surface geopotential heights m2 / s2
PS I-6 2D Surface pressure mb
SLP I-6 2D Sea level pressure mb
CLDTOT A-6 3D 3D cloud fraction (conv + large scale) unitless
HKBETA A-6 3D Hack overshoot parameter unitless
HKETA A-6 3D Hack convective mass flux kg / m2 / s
MOISTQ A-6 3D Tendency in specific humidity g H2O / kg air / day
OPTDEPTH A-6 3D Grid box optical depth unitless
Q A-6 3D Specific humidity g H2O / kg air
T A-6 3D Temperature K
U A-6 3D Zonal wind m / s
V A-6 3D Meridional wind m / s
ZMEU A-6 3D Zhang-McFarlane updraft entrainment Pa / s
ZMMD A-6 3D Zhang-McFarlane downdraft mass flux Pa / s
ZMMU A-6 3D Zhang-McFarlane updraft mass flux Pa / s
ALBEDO A-3 2D Surface albedo (visible) unitless
CLDFRC A-3 2D Column cloud fraction at ground unitless
GWETTOP A-3 2D Top soil wetness unitless
HFLUX A-3 2D Sensible heat flux W / m2
LAI A-3 2D Leaf area indices %
PARDF A-3 2D Photosynthetically active diffuse radiation W / m2
PARDR A-3 2D Photosynthetically active direct radiation W / m2
PBLH A-3 2D Planetary boundary layer depth m
PREACC A-3 2D Total precipitation at ground mm H2O / day
PRECON A-3 2D Convective precipitation at ground mm H2O / day
RADLWG A-3 2D Longwave (IR) radiation emanating from the ground W / m2
RADSWG A-3 2D Solar Insolation (shortwave) reaching the ground W / m2
SNOW A-3 2D Snow depth (equivalent water) mm H2O
T2M A-3 2D Air temperature at 2 meter elevation K
TSKIN A-3 2D Skin temperature (ground T or sea surface T) K
U10M A-3 2D UWND at 10 m altitude m / s
USTAR A-3 2D Friction velocity m / s
V10M A-3 2D VWND at 10 m altitude m / s
Z0M A-3 2D Roughness height m

NOTES for GEOS–4 fields:

  1. GEOS–4 I-6 fields contain instantaneous ("snapshot") data, at 00, 06, 12, and 18 GMT. GEOS–CHEM linearly interpolates these to intermediate times.

  2. GEOS–4 A-6 fields (a_llk_03 dataset) contain 6-hour average data, centered at 03, 09, 15, and 21 GMT. For example, an A-6 data field timestamped 03 GMT is an average between 00 GMT and 06 GMT.

  3. GEOS–4 A-6 fields (a_llk_04 dataset) contain 6-hour average data, centered at 00, 06, 12, and 18 GMT. For example, an A-6 data field timestamped 06 GMT is an average between 03 GMT and 09 GMT.

  4. GEOS–4 A-3 fields contain 3-hour average data, centered at 01:30, 04:30, 07:30, 10:30, 13:30, 16:30, 19:30, and 22:30 GMT. For example, an A-3 data field timestamped 01:30 GMT is an average from 00 GMT to 03 GMT.

  5. In GEOS–1, GEOS–STRAT, and, GEOS–3, specific humidity was an I-6 field; in GEOS-4 it is an A-6 field.

  6. In GEOS–1, GEOS–STRAT, and, GEOS–3, temperature was an I-6 field; in GEOS-4 it is an A-6 field.

  7. In GEOS–1, GEOS–STRAT, and, GEOS–3, zonal wind was an I-6 field; in GEOS-4 it is an A-6 field.

  8. In GEOS–1, GEOS–STRAT, and, GEOS–3, meridional wind was an I-6 field; in GEOS-4 it is an A-6 field.

  9. In GEOS–1, GEOS–STRAT, and, GEOS–3, surface albedo was an I-6 field; in GEOS-4 it is an A-3 field.

  10. The air temperature at 2 meters is used as a proxy for the surface air temperature.

  11. Skin temperature is the temperature of the ground (or ocean) surface. This is required for the new isoprene emissions mechanism which is currently under development.

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