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The output is a collection of per-variable timeseries such as FSNT_YYYYMM_YYYYMM.nc, AODVIS_YYYYMM_YYYYMM.nc, etc. The output is split into segments each containing no more than ypf_max (default 50) years-per-file, e.g., FSNT_000101_005012.nc, FSNT_005101_009912.nc, FSNT_010001_014912.nc, etc. Change the maximum number of years-per-output-file with the --ypf_max=ypf_max option. One caveat worth noting is that, for technical reasons, non-interactive batch queues cannot unambiguously distinguish filelists provided via stdin from batch queue information provided via stdin. To address this issue, ncclimo supports the --stdin switch to cause the filelist to be read from stdin. This switch is only necessary when running ncclimo in non-interactive batch mode. The switch is permitted though redundant when running ncclimo interactively (i.e., from a terminal shell). The remainder of the ncclimo documentation refers to climatology-generation mode, not to splitter mode.
Climatology generation mode (produce monthly
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, seasonal
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, and annual
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climatologies from monthly-mean input
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data)
The usual way to use A common task for ncclimo is to bring up a terminal window and typeproduce climatological monthly, seasonal, and annual-means from an interannual series of monthly-mean input files with commands like these:
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ncclimo -s start_yr -e end_yr -c run_id -i drc_in -o drc_out # EAM/CAM/CAM-SE ncclimo -v FSNT -s start_yr -e end_yr -c run_id -i drc_in -o drc_out # EAM subset ncclimo -m clm2 -s start_yr -e end_yr -c run_id -i drc_in -o drc_out # ELM/ALM/CLM |
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When invoked without options ncclimo outputs a handy table of all available options, their long-option synonyms, and some examples. NCO documentation here describes the full meaning of all options. A short summary of the The most common options isare:
-a, --dec_md: The “December mode” specifies the desired type of DJF average. Either -a sdd (default) or -a scd. scd means seasonally continuous December. The first month used will be Dec of the year before the start year you specify with -s. sdd means seasonally discontinuous December. The first month used will be Jan of the specified start year. (Prior to NCO 4.9.4, released in August 2020, the default was scd not sdd.)
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-o, --drc_out: Directory where computed native grid climo files will be placed. Regridded climos will also be placed here unless a separate directory for them is specified with -O (NB: capital "O")
-O, --drc_rgr: directory Directory where regridded climo files will be placed.
-s, --yr_srt: start Start year (example: 1980). By default, the first month used will be Jan of this start year. If -a scd is specified, the first month used will be Dec of the year before this specified start year (example Dec 1979 to allow for contiguous DJF climos).
-v, --var: variable Variable list to subset, e.g., FSNT,AODVIS,PREC.? (yes, regular expressions work so this expands to PRECC,PRECL,PRECSC,PRECSL)
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If/when MPAS generates the _FillValue attributes itself, this step can and should be skipped. All other ncclimo features like regridding (below) are invoked identically for MPAS as for EAM/ELM users although under-the-hood ncclimo does do some special pre-processing (dimension permutation, metadata annotation) for MPAS. A five-year oEC60to30 MPAS-O climo with regridding to T62 takes < 10 minutes on rhea.
High Frequency climos (produce climotological means of diurnal cycles from diurnally resolved input data)
As of NCO 4.9.4 (September, 2020), ncclimo will produce climatologies that retain the diurnal cycle resolution provided by the input data. These “high frequency climos” are useful for characterizing the diurnal cycle of processes typically retained in EAM/ELM h1-h4 history output, observational reanalyses (e.g., MERRA2, ERA5), and similar data.
Annual climos (produce
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climotological means from annual-mean input
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data)
Not all model or observed history files are created as monthly means. To create a climatological annual mean from a series of annual mean inputs (such as from a land ice model), select ncclimo's annual climatology mode with the -C ann option:
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The options -m mdl_nm and -h hst_nm (that default to "cam" and "h0", respectively) tell ncclimo how to construct the input filenames. The above formula names the files caseid.cism.h.1851-01-01-00000.nc, caseid.cism.h.1852-01-01-00000.nc, and so on. Annual climatology mode produces a single output file (or two if regridding is selected), and in all other respects behaves the same as monthly climatology mode.
Daily climos (interannual day-of-year statistics from multi-year daily-to-
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diurnally-
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resoluved input
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data)
High frequency timeseries are often available as daily means. To create a climatological daily mean from a series of daily mean inputs, select daily mode with the "--clm_md=dly" option. What is computed? In daily mode ncclimo produces 365 output files, each consisting of the interannual average of the given day-of-year. If the input data are at sub-daily resolution (e.g., 8 timesteps per day for three hourly data), then by default all timesteps in a day are averaged into the daily output. An option to preserve the diurnal cycle for each day is in the works, contact Charlie Zender if interested. Also on the drawing board is a simple method to obtain min/max/avg etc. at the same time, or at least with the same command.
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