data.exoprt

The data.exoprt file is used to control the radiative transfer bit of expeRT/MITgcm. This is an example file:

C--   Full radiative transfer input:
# EXORAD_DAY_DT :: radiative timestep for dayside (needs to be multiple of deltaT)
# EXORAD_NIGHT_DT :: radiative timestep for nightside (needs to be multiple of deltaT)
# EXORAD_INTERP_STEP :: radiative interpolation step (should be 1 or 2). 1 = No interpolation, 2 = every second column
# EXORAD_SCATTERING  :: scattering flag. If set to False, we will not use scattering. Warning: only set to false if photon_destruct_prob = 1 and opac_scat = 0!
# EXORAD_MAX_I_ITER_SCAT :: max. amount of iterations performed to converge the source function
# EXORAD_MAX_REL_DELTA_S :: convergence criterion for the convergence of the source function
# EXORAD_MIN_TEMP :: minimal temperature, where the GCM will stop forcing to cooler temperatures (we dont want negative temperatures)
# EXORAD_INTERP_METH :: interpolatation method of temperature to cell interfaces, if you set it to one, it will use the Bezier interpolation, else it will use a linear interpolation
# EXORAD_TINT :: interior temperature to force bottom boundary flux. If set to neg. values, it will not set the boundary fluxes.

 &EXORAD_PRT
 EXORAD_deltaT = 100.0,
 EXORAD_INTERP_STEP = 2,
 EXORAD_SCATTERING = .TRUE.,
 EXORAD_MAX_I_ITER_SCAT = 500,
 EXORAD_MAX_REL_DELTA_S = 0.02,
 EXORAD_MIN_TEMP = 50.0,
 EXORAD_INTERP_METH = 1,
 EXORAD_TINT = -1.0,
 &


C-- Chemistry in radiative transfer
# EXORAD_MIX_METHOD       :: Opacity mixing method, if mixing is enabled (ALLOW_EXORAD_MIX), -1 (or anything else) is RORR, 0 is adding up, 1 is ML mixing, 2 is AEE
# EXORAD_CHEM_METHOD      :: disequilibrium chemistry method to use (1=rainout, choose anything else for no diseq)
 &EXORAD_CHEM
 EXORAD_MIX_METHOD = -1
 EXORAD_CHEM_METHOD = -1
 &

Clearly, the most important parameter in this file is EXORAD_deltaT, which sets the frequency of flux updates (the radiative timestep). High values in EXORAD_deltaT may lead to incorrect radiative fluxes that would cause the model to heat/cool to unphysical temperatures, which could cause crashes.

Note

If you encounter crashes in your model, you might want to lower the value of EXORAD_deltaT.

Note

EXORAD_INTERP_METH and EXORAD_TINT are new parameters. Handle with caution. Using EXORAD_INTERP_METH=1 should increase the stability of the model.

Warning

EXORAD_deltaT needs to be a multiple of the dynamical timestep!

You can turn on or off scattering with the EXORAD_SCATTERING flag. The convergence behaviour of the source function is controlled with EXORAD_MAX_I_ITER_SCAT and EXORAD_MAX_REL_DELTA_S. For more information on the convergence of the source function see Schneider et al. (2022). EXORAD_INTERP_STEP controls whether you interpolate fluxes horizontally or not. For more information on the interpolation of fluxes see Schneider et al. (2022).

All parameters in the EXORAD_CHEM namelist are only used if #define ALLOW_EXORAD_MIX has been set in code/EXORAD_OPTIONS.h. If this wasn’t set, it will as default use the premixed opacity tables. You can decide with EXORAD_MIX_METHOD which method to use for the k-table mixing. See Schneider et al. (2023) for a discussion of the implemented methods.