Stratospheric-adjusted radiative forcing in GC-Classic (supersedes PR #2525)

[yantosca]

Name and Institution

Name: Bob Yantosca (Harvard) on behalf of Connor Barker (UCL) and Eloise Marais (UCL)

NOTE: We have rebased the code from PR #2525 (by @cbarker211) atop GEOS-Chem 14.7.0. This PR now supersedes #2525 which will be closed.

Describe the update

This update extends the stratospheric adjustment code added by @sdeastham in GCHP (#2010) to GCClassic. The commit here simply modifies the main level script for GCClassic, and allows the dynamical heating rates to be read in via the HEMCO meteorology file. No changes are made to the underlying RRTMG source code beyond what Seb already has added to include stratospheric adjustment. For further details see the original pull request.

To include stratospheric adjustments of temperature relative to the baseline simulation in the radiative fluxes, follow these steps:

• Run a baseline simulation with no pertubations.

  • Set the following in geoschem_config.yml (rrmtg must be activated):
    • fixed_dyn_heating: true
    • read_dyn_heating: false
    • Activate the DynHeating collection in HISTORY.rc (sample file provided below) - this outputs the dynamical heating rates.

• Run a pertubation simulation.

  • Create a symbolic link in the run directory called Heating_Baseline to point to the DynHeating output from the baseline simulation:
    • e.g. ln -s /path/to/reference/rundir/OutputDir Heating_Baseline
  • Set the following in geoschem_config.yml (rrmtg must be activated):
    • fixed_dyn_heating: true
    • read_dyn_heating: true
  • Add the following to the HEMCO_Config.rc.gmao_metfields file - this loads the dynamical heating rates:

# --- DynHeating field ---
* DynHeating  ./Heating_Baseline/GEOSChem.DynHeating.$YYYY$MM$DD_$HH00z.nc4 DynHeating 2019/1-12/1-31/0-23 I xyz 1 * - 1 1

HISTORY.txt

As described in #2010, occasionally there will be a warning of "RRTMG FDH routine failed to converge for x of y columns on CPU 0". We find this happens sporadically for our simulations for 1/3312 columns. Failing to converge for >10 columns usually indicates an error somewhere.

The seasonally-evolving fixed dynamical heating approximation has also been extended to GCClassic, but is not yet tested (as stated by Seb in #2010). The fdh_to_toa flag can be added in geoschem_config.yml to extend the stratospheric adjustment calculations to the top of the model.

Expected changes

This code can be tested by simulating a single day with and without an increase of 100 ppmv CO2 (see #2010).

    - 20190701 - 20190702, no spinup, default restart file.
    - 4 simulations:
        - baseline   (co2_ppmv: 390.0, read_dyn_heating: false)
        - without_sa (co2_ppmv: 490.0, read_dyn_heating: false)
        - sa_strat   (co2_ppmv: 490.0, read_dyn_heating: true, fdh_to_toa: false)
        - sa_toa     (co2_ppmv: 490.0, read_dyn_heating: true, fdh_to_toa: true)
    - If successful, you should get the following results.  
        -           Sim  TOA RF / W m-2  Trop CO2 RF / W m-2  TOA RF - Trop RF / W m-2
         0        No SA            0.64                 1.25                     -0.61
         1  SA in strat            1.10                 1.24                     -0.09
         2    SA to TOA            1.16                 1.24                     -0.02
        - The expected changes are an increase in the TOA RF, and a small decrease in the Trop CO2 RF. 

References

• See Stratospheric adjustment and additional output fields for RRTMG in GCHP #2010
• See Extending Stratospheric Adjustment to GCClassic #2525

Tagging @cbarker211 @eamarais

[yantosca]

I ran an integration test on the feature/strat-adjusted-rf branch. All GEOS-Chem Classic integration tests passed:

==============================================================================
GEOS-Chem Classic: Execution Test Results

CodeDir   : 7ce5cb9 GEOS-Chem update: Merge PR #3138 (Diagnostic timestep update)
GEOS-Chem : 7dc642f80 Move array alloc/dealloc for strat-adjusted rf to routines in main.F90
HEMCO     : e23c43b HEMCO 3.12.0 release
Cloud-J   : 1dff6fe Merge pull request #31 from geoschem/release/8.0.2
HETP      : 2a99b24 Merge pull request #2 from geoschem/bugfix/initialize_local_variables

Using 24 OpenMP threads
Number of execution tests: 38

Submitted as SLURM job: 61416506
==============================================================================

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%  All execution tests passed!  %%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

All GEOS-Chem Classic tests were zero-diff w/r/t gcc.14.7.0, except:

• gc_4x5_merra2_fullchem_APM
  • Parallel error (known issue)

[msulprizio]

Is there a reason why this code is in main.F90 and not in an RRTMG module? It seems out of place here.

[yantosca]

@msulprizio It's how it came to us. Maybe this can be moved.

[msulprizio]

Thanks @yantosca. I really don't think it makes sense to have code specific for RRTMG in main.F90. I would recommend moving routines Init_RRTMG_Strat_Adj_RF and Cleanup_RRTMG_Strat_Adj_RF from Interfaces/GCClassic/main.F90 to GeosCore/rrtmg_rad_transfer_mod.F90. It will just need to be checked that this doesn't conflict with Interfaces/GCHP/gchp_chunk_mod.F90 or else block off with an #ifdef.