README.md

In ECA-D/ecad_indices_grid: Functions to compute CLIMIND indices over a NetCDF grid

gridclimind

climate indices tool for E-OBS data (used only with ecad_indices_stations)

Common tasks

Add new index

For an example of how to add indices from climind into gridclimind you can have a look at the 7d185d65 commit in gridclimind (‘Added last three compound indices…etc’). In general, adding an index you will have to take the following steps:

1. Add a function to climind which uses the correct interface, i.e.:

   function(ci, freq=c("annual”), cur_sub)
   

   Where:

   • ci is the input object, this will be provided by gridlcimind.
   • freq the supported list of time resolutions. Typically this will be freq=c("monthly", "annual", "halfyear", "seasonal”).
   • additional arguments needed. Note that in general these can only be static arguments either having a default value or a static value defined in the json file.

2. Add the metadata information to eobs.json (inst/extdata/metadata_config_files in the gridclimind project) in the index.metadata list. For example:

   "csdi": {
     "long.name": "Cold Spell Duration Index",
     "units": "days",
     "base.period.attr": true,
     "standard.name": "cold_spell_duration_index",
     "calculation.function.name": "climdex.csdi",
     "additional_arguments": {
       "spells.can.span.years": false
     },
     "supported.time.resolutions": "annual",
     "include.time.prefix.in.long.name": true,
     "required.variables": "tmin"
   }
   

   Note that:

   • additional_arguments is optional. These extra input arguments are fed to the listed calculation.function.name, i.e. the new function we created in step 1.
   • supported.time.resolutions and required.variables can also be a list of values, e.g.:

     "ww": {
       "long.name": "Warm-wet days",
       "units": "",
       "base.period.attr": false,
       "standard.name": "warm_wet_days",
       "calculation.function.name": "climdex.wd",
       "additional_arguments": {
         "precip.thresh": "q75",
         "precip.op": ">",
         "temp.thresh": "q75",
         "temp.op": ">"
       },
       "supported.time.resolutions": ["annual", "monthly", "seasonal", "halfyear"],
       "include.time.prefix.in.long.name": true,
       "required.variables": ["prec", "tavg"]
     }
     

3. Add the index file to the test suite:

   1. Run the test manually.

   2. Go to the output directory, this is listed in the output_data_path variable, e.g.:

      output_data_path
      [1] "/var/folders/dm/smk5_rf53bg057ql34rmhnq80000gn/T//RtmpphG0Nw"
      

      Copy the nc file for the index you added to /your/installation/of/gridclimind/tests/testthat/reference_ncfiles/generate_all_indices_test/. This could be up to 4 files, depended on the supported time resolutions. 3. The reference rds files for the metadata test will change probably. After checking that the change is really related to the addition of a new index, simply delete the offending rds files and rerun the test. This will generate new reference files which contain the new index.

   3. Commit the changes in the gridlcimind package to git.

Add new variable

The list of variables that gridclimind is aware of is stored in the metadata json file under generic.metadata$variable.name.map. There you list how each of the possible input variables is called in the input NetCDF files. Some important notes:

• the names you use in the variable.name.map on the left hand side need to match those used in gridclimind and climind. A good resource here is the climind::climdexInput.raw function which uses all of these names.
• If a variable is not supported by climind::climdexInput.raw there is no way to calculate the indices. You can read the data from the input NetCDF files, but there will be no way to build the input data object for the indices. So, you need to add support for a variable to climind first and then add it to the gridclimind variable.name.map.

ECA-D/ecad_indices_grid documentation built on Nov. 23, 2022, 6:04 a.m.