Run CABLE-POP at ACCESS Resolution

Land Surface CABLE
2

TRENDY forcing requirements and CMOR equivalents
There are (up to) 11 forcing variables needed to run CABLE-POP in the TRENDY set up. Of these 8 are readily available (i.e. at the correct temporal resolution, gridded, for at least 1950 onwards) via the CMIP6 CMOR archive on fs38 (historical simulation), 1 variable is available but would require further processing, 1 requires further thought and 1 is unavailable.

The 8 variables available are [TRENDY netcdf name, CMOR name, {CMOR section}]

  1. daily total precipitation flux [rain, pr, {day}]
  2. daily downwelling longwave radiation at the surface [dlwrf, rlds, {day}]
  3. daily total downwelling shortwave radiation at the surface [tswrf, rsds, {day}]
  4. daily averaged (2m) specific humidity [spfh, huss, {day}]
  5. daily maximum (2m) air temperature [tmax, tasmax, {day}]
  6. daily minimum (2m) air temperature [tmin, tasmin, {day}]
  7. daily (10m) easterly wind component [ugrd, uas, {day}]
  8. daily (10m) northerly wind component [vgrd, vas, {day}]

These variables would need some attention to change variable names and check units. The wind variables could be substituted for the CMOR variable sfcWind (and a set of zeros) if sensible.

The variable requiring further processing is

  • daily surface pressure [pres, surface value of the 3D field ps]

ps (and specifically the surface value of ps - which should not be substituted by the mean sea level pressure psl) is a variable in the {CFday} section but does not appear to have been archived on fs38. However ps has been archived at 6-hourly intervals in the {6hrLev} section. It should be relatively simple to post-process this to an appropriate daily averaged, surface level variable.

The variable(s) that requires further thought are

  • atmospheric CO2 (in ppm) - the TRENDY configuration uses a single, annual and globally average value. The ESM could provide interactive temporo-spatial fields, CM2/CM3 will be using prescribed time series.
  • Nitrogen deposition and other scenario dependent ancillaries.

The variable that is not available in CMOR (and hence fs38) is

  • fraction of downwelling shortwave radiation that is diffuse [df].

This variable could be constructed from CMOR variables rsdsdiff and rsds, however rsdsdiff does not appear to have been archived.

Note: This variable is not compulsory for TRENDY (prior to TRENDY v11 this input was not available) and the code can default to using a fixed fraction (50:50 direct:diffuse) if this is not supplied. Hence, for our purposes (testing and spin up), the lack of a true input for [fd] is unlikely to be critical.

Some post-processing is likely required for all variables to ensure that the grid is compatible (e.g. the appropriate latitude, longitude ranges are used, ensure date-time is as expected, appropriate metadata is embedded) and (potentially) to concatenate the CMOR files into longer time series.

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