Radiative transfer with RRTMG
On this page we provide information about the coupling of GEOS-Chem with the RRTMG radiative transfer model (by AER, Inc.).
Overview
The GEOS-Chem model with online radiative transfer calculations was developed to allow GEOS-Chem users to produce gas and aerosol direct radiative effect (DRE) output for both the longwave and shortwave. This alternative to offline coupling allows better temporal resolution in the RT calculations and provides a consistent platform for GEOS-Chem users with the widely used radiative transfer package RRTMG.
Most of the added code is ‘transparent’, therefore this version of the GEOS-Chem model can still be run with the radiation code switched off. The optical properties are calculated at multiple wavelengths so that the user is no longer restricted to 550 nm as default, so there are associated changes regardless of whether the radiative code is invoked. However, these cause negligible slowdown (the default model Compiling with -DRRTMG=y requires approximately double the amount of RAM and takes between 40% and 100% longer depending on the settings used.
Reference: Heald et al. [2014]
Important notes
A menu for Radiation exists in Settings in geoschem_config.yml. This also includes a wavelength selection for optical depth output that is independent of whether RRTMG is switched on (up to three optical depths can be output in the HISTORY diagnostics).
A code folder,
GeosRad/is required for the RRTMG code. The modulerrtmg_rad_transfer_mod.F90is the driver code (found inGeosCore/) that interfaces with RRTMG.
The optics look-up tables are updated, containing multiple wavelengths and separated into files for each species (
soot.dat,so4.dat,org.dat,dust.dat,ssa.dat,ssc.dat) that are stored in the Aerosol Optics folder (specified ingeoschem_config.ymlhere:aerosols: optics: input_dir: /path/to/Aerosol_Optics/folder
Surface albedo and emissivity climatologies have been generated and must be stored in the HEMCO data path(e.g.,
ExtData/HEMCO/RRTMG/v2018-11).Diagnostics are available providing the change in radiative flux (DRE) for gases and aerosol, LW/SW, top of atmosphere (TOA) and surface, and clear-sky and all-sky conditions. These also include AOD, SSA, and asymmetry parameter for each aerosol species at the requested wavelengths.
Running GEOS-Chem with RRTMG
_rrtmg-guide-running-species:
Available species
The species available for output from the flux calculations are as follows:
# |
Abbreviation |
Species |
|---|---|---|
0 |
BA |
Baseline calculation |
1 |
O₃ |
Ozone |
2 |
ME |
Methane |
3 |
SU |
Sulfate |
4 |
NI |
Nitrate |
5 |
AM |
Ammonium |
6 |
BC |
Black carbon |
7 |
OA |
Organic aerosol |
8 |
SS |
Sea salt |
9 |
DU |
Mineral dust |
10 |
PM |
All particulate matter |
11 |
ST |
Stratospheric aerosol |
Note
The radiative impacts of gases (ozone and methane) are relatively untested at this stage and should be interpreted with caution.
Settings in geoschem_config.yml
For more information about these settings, please see the geoschem_config.yml chapter in our ReadTheDocs documentation.
#============================================================================
# Timesteps settings
#============================================================================
timesteps:
transport_timestep_in_s: 600
chemistry_timestep_in_s: 1200
radiation_timestep_in_s: 10800 # <=== timestep for RRTMG
#============================================================================
# Settings for GEOS-Chem operations
#============================================================================
operations:
.. etc ...
rrtmg_rad_transfer_model:
activate: true
aod_wavelengths_in_nm:
- 550
longwave_fluxes: true
shortwave_fluxes: true
clear_sky_flux: true
all_sky_flux: true
fixed_dyn_heating: false
seasonal_fdh: false
read_dyn_heating: false
co2_ppmv: 390.0
Settings in HEMCO_Config.rc
Several of the inputs to RRTMG are stored in netCDF format for input via HEMCO. These include:
Diffuse surface albedos in visible and near-IR
Direct surface albedos in visible and near-IR
Surface emissivity in 16 different wavelength bands
Concentrations of CCl₄, CFC-11, CFC-12, CFC-22, CH₄, N₂O from TES in ppb
You will see lines similar to this in the HEMCO_Config.rc file
that ships with the RRTMG simulation run directory:
#==============================================================================
# --- Inputs for the RRTMG radiative transfer model ---
#
# NOTE: The 2 x 2.5 albedo fields and emissivity fields will produce
# differences at the level of numerical noise when comparing output to
# simulations from prior versions (esp. when running at 4 x 5 resolution).
# You might see larger differences w/r/t prior versions for a few grid boxes
# along the coastline of Antarctica, where the difference in resolution
# and regridding will be more apparent in the sharp transition from ice to
# ocean. If this is a problem, you can use the data files at 4x5 resolution
# for 4x5 RRTMG simulations.
#
# ALSO NOTE: The algorithm that HEMCO uses to select each time slice is
# likely different than what was implemented when reading the old bpch
# data from disk. This can also cause differences when comparing to
# prior versions.
#==============================================================================
(((RRTMG
* MODIS_ALBDFNIR $ROOT/RRTMG/v2018-11/modis_surf_albedo.2x25.nc ALBDFNIR 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_ALBDFVIS $ROOT/RRTMG/v2018-11/modis_surf_albedo.2x25.nc ALBDFVIS 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_ALBDRNIR $ROOT/RRTMG/v2018-11/modis_surf_albedo.2x25.nc ALBDRNIR 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_ALBDRVIS $ROOT/RRTMG/v2018-11/modis_surf_albedo.2x25.nc ALBDRVIS 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_01 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band01 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_02 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band02 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_03 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band03 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_04 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band04 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_05 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band05 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_06 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band06 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_07 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band07 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_08 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band08 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_09 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band09 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_10 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band10 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_11 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band11 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_12 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band12 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_13 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band13 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_14 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band14 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_15 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band15 2002/1-12/1-31/0 C xy 1 * - 1 1
* MODIS_EMISSIVITY_16 $ROOT/RRTMG/v2018-11/modis_emissivity.2x25.nc RTEMISS_band16 2002/1-12/1-31/0 C xy 1 * - 1 1
* TES_CLIM_CCL4 $ROOT/RRTMG/v2018-11/species_clim_profiles.2x25.nc CCl4 2000/1/1/0 C xyz ppbv * - 1 1
* TES_CLIM_CFC11 $ROOT/RRTMG/v2018-11/species_clim_profiles.2x25.nc CFC11 2000/1/1/0 C xyz ppbv * - 1 1
* TES_CLIM_CFC12 $ROOT/RRTMG/v2018-11/species_clim_profiles.2x25.nc CFC12 2000/1/1/0 C xyz ppbv * - 1 1
* TES_CLIM_CFC22 $ROOT/RRTMG/v2018-11/species_clim_profiles.2x25.nc CFC22 2000/1/1/0 C xyz ppbv * - 1 1
* TES_CLIM_CH4 $ROOT/RRTMG/v2018-11/species_clim_profiles.2x25.nc CH4 2000/1/1/0 C xyz ppbv * - 1 1
* TES_CLIM_N2O $ROOT/RRTMG/v2018-11/species_clim_profiles.2x25.nc N2O 2000/1/1/0 C xyz ppbv * - 1 1
)))RRTMG
The data files are located in the HEMCO/RRTMG/v2018-11 folder on our
GEOS-Chem Input data portal.
Settings in HISTORY.rc
#==============================================================================
# %%%%% THE RRTMG COLLECTION %%%%%
#
# Outputs for different species from the RRTMG radiative transfer model:
# (See http://wiki.geos-chem.org/Coupling_GEOS-Chem_with_RRTMG)
#
# 0=BA (Baseline ) 1=O3 (Ozone ) 2=ME (Methane )
# 3=SU (Sulfate ) 4=NI (Nitrate ) 5=AM (Ammonium )
# 6=BC (Black carbon) 7=OA (Organic aerosol) 8=SS (Sea Salt )
# 9=DU (Mineral dust) 10=PM (All part. matter) 12=ST (Strat aer., UCX only)
#
# NOTES:
# (1) Only request diagnostics you need to reduce the overall run time.
# (2) The ?RRTMG? wildcard includes all output except ST (strat aerosols).
# However, if ST is included explicitly for one diagnostic then it
# will be included for all others that use the wildcard.
# (3) Only enable ST if running with UCX.
# (4) Optics diagnostics have a reduced set of output species (no BASE, O3, ME)
#==============================================================================
RRTMG.template: '%y4%m2%d2_%h2%n2z.nc4',
RRTMG.frequency: 00000000 010000
RRTMG.duration: 00000000 010000
RRTMG.mode: 'time-averaged'
RRTMG.fields: 'RadClrSkyLWSurf_BASE ',
'RadClrSkyLWSurf_O3 ',
'RadClrSkyLWSurf_ME ',
'RadClrSkyLWSurf_SU ',
'RadClrSkyLWSurf_NI ',
'RadClrSkyLWSurf_AM ',
'RadClrSkyLWSurf_BC ',
'RadClrSkyLWSurf_OA ',
'RadClrSkyLWSurf_SS ',
'RadClrSkyLWSurf_DU ',
'RadClrSkyLWSurf_PM ',
#'RadClrSkyLWSurf_ST ',
'RadAllSkyLWSurf_?RRTMG?',
'RadClrSkySWSurf_?RRTMG?',
'RadAllSkySWSurf_?RRTMG?',
'RadClrSkyLWTOA_?RRTMG? ',
'RadAllSkyLWTOA_?RRTMG? ',
'RadClrSkySWTOA_?RRTMG? ',
'RadAllSkySWTOA_?RRTMG? ',
'RadAODWL1_SU ',
'RadAODWL1_NI ',
'RadAODWL1_AM ',
'RadAODWL1_BC ',
'RadAODWL1_OA ',
'RadAODWL1_SS ',
'RadAODWL1_DU ',
'RadAODWL1_PM ',
#'RadAODWL1_ST ',
'RadSSAWL1_SU ',
'RadSSAWL1_NI ',
'RadSSAWL1_AM ',
'RadSSAWL1_BC ',
'RadSSAWL1_OA ',
'RadSSAWL1_SS ',
'RadSSAWL1_DU ',
'RadSSAWL1_PM ',
#'RadSSAWL1_ST ',
'RadAsymWL1_SU ',
'RadAsymWL1_NI ',
'RadAsymWL1_AM ',
'RadAsymWL1_BC ',
'RadAsymWL1_OA ',
'RadAsymWL1_SS ',
'RadAsymWL1_DU ',
'RadAsymWL1_PM ',
#'RadAsymWL1_ST ',