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-a, --dec_md: The “December mode” specifies the desired type of DJF average. Either -a sdd (default) or -a scd. scd means option determines the start and end months of the climatology and the type of NH winter seasonal average. Valid arguments are sdd (default, or synonyms jfd and JFD) and scd (or synonyms djf and DJF). scd stands for seasonally continuous December. The first month used will be Dec of the year before the start year you specify with -s. The last month is November of the end year specified with -e. sdd means In SCD-mode the Northern Hemisphere winter seasonal climatology will be computed with sets of the three consecutive months December, January, and February (DJF) where the calendar year of the December months is always one less than the calendar year of January and February. sdd stands for seasonally discontinuous December. The first month used will be Jan of the specified start year. The last month is December of the specified end year. In SDD-mode the Northern Hemisphere winter seasonal climatology will be computed with sets of the three non-consecutive months January, February, and December (JFD) from each calendar year. (Prior to NCO 4.9.4, released in August 2020, the default was scd not sdd.)
-C, --clm_md: Climatology mode. Either mth (default, and for indicates monthly-mean input files), hfc for high-frequency-climo (i.e., diurnal cycles from sub-daily input files), hfs for high-frequency-splitter (i.e., concatenation of sub-daily . input files), or ann (for annual-mean input files).
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