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CFMIP Observation Simulator Package (COSP) in EAMxx

COSP is partially implemented and supported in EAMxx. Currently, minimal outputs from the ISCCP, MODIS, and MISR simulators have been enabled.

Running with COSP

Turning COSP on simply requires adding the cosp process to atm_procs_list via atmchange in a case directory: 

./atmchange physics::atm_procs_list="mac_aero_mic,rrtmgp,cosp"
Additionally, the frequency at which COSP is run can be configured via atmchange: 
./atmchange physics::cosp::cosp_frequency_units="steps"
./atmchange physics::cosp::cosp_frequency=1

COSP can be run with or without subcolumn sampling. This is configured by changing the cosp_subcolumns namelist variable via atmchange. A value of 1 implies no subcolumn sampling, while values greater than 1 specify the number of subcolumns to use for subcolumn sampling (assuming maximum-random overlap). E.g., 

./atmchange physics::cosp:cosp_subcolumns=1
would disable subcolumn sampling, while 
./atmchange physics::cosp::cosp_subcolumns=10
would use 10 subcolumns for the COSP internal subcolumn sampling using SCOPS/PREC_SCOPS. The default for high resolution cases (e.g., ne1024) should be to not use subcolumns, while lower resolutions (e.g., ne30) should enable subcolumn sampling.

Output streams need to be added manually. A minimal example: 

./atmchange output_yaml_files=scream_daily_output.yaml
cat << EOF > scream_cosp_daily_output.yaml
Averaging Type: Average
Fields:
  Physics PG2:
    Field Names:
    - isccp_cldtot
    - isccp_ctptau
    - modis_ctptau
    - misr_cthtau
    - cosp_sunlit
Max Snapshots Per File: 1
filename_prefix: eamxx
output_control:
  Frequency: 1
  frequency_units: ndays
EOF

Available output fields

The following output fields are available:

  • isccp_cldtot (total cloud area from ISCCP simulator)
  • isccp_ctptau (ISCCP-simulated cloud top pressure/optical depth joint histogram)
  • modis_ctptau (MODIS-simulated cloud top pressure/optical depth joint histogram)
  • misr_cthtau (MISR-simulated cloud top height/optical depth joint histogram)
  • cosp_sunlit (sunlit flag aggregated at COSP frequency for renormalizing daytime averages)

ISCCP, MODIS, and MISR outputs are valid only for daytime/sunlit columns (to be consistent with available satellite retrievals). In order to aggregate only daytime columns in time averages, these outputs are multiplied by the sunlit flag (0 or 1) at each COSP calculation time. Time averages of these quantities are then aggregated, along with the cosp sunlit flag each time COSP is called. In order to back out the daytime-only time averages from the outputs, one needs to divide the output fields by cosp_sunlit. E.g., 

isccp_ctptau = mean(isccp_ctptau) / mean(cosp_sunlit)