Concatenate AMIP Ancillaries

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The ancillary values used for AMIP model runs come in two sections - historical values and RCP projections. The crossover between these sections happens between the years 2000 and 2002, with the RCP files beginning in January 2000 and the historical values ending in December 2001.

For AMIP model runs going over this date range either the job need to be stopped, the ancillary files changed over and the the job restarted or the two ancillary sections need to be combined.

The AMIP ancillary files can be found in ~access/data/ancil/CMIP5. The following ancillary categories are available for the RCP scenarios:

BC_hi: Soot
BIO:   Biomass emissions
OCFF:  Organic carbon & fossil fuels
sulp:  Sulphyr emissions

To create a combined file following the full range:

1. Convert both segments to netcdf (e.g. with xconv)

2. Trim the ancillary files so that the date ranges don't overlap


cdo selyear,2002/2100

3. Concatenate the two netcdf segments



4. Use xancil to convert the concatenated netcdf file to UM format

  • Make sure to set the version in Configuration/General to 7.3
  • Use the 'generalised ancillary' section. Add the netcdf file and select the variables, the STASH code should get filled in automatically.
  • You may need to override the dates in the file, specifying the start date and interval (1 month)
    • To get values on the 16th of each month with a Gregorian calendar generate the ancillary using a 360 day calendar, then post-process by running


python ~access/apps/pythonlib/umfile_utils/ ANCIL

Check the ancillary file using xancil, making sure the field & dates are correct