Skip to contents

Convert climate data to seasonal frequency

Source: R/htr_seasonal_frequency.R
htr_seasonal_frequency.Rd

This function converts monthly or daily climate data to seasonal averages by selecting specific months and calculating their yearly means using CDO (Climate Data Operators). This is useful for analyzing seasonal climate patterns and reducing temporal resolution for specific seasonal analyses.

Usage

htr_seasonal_frequency(
  hpc = NA,
  file = NA,
  indir,
  tempdir,
  outdir,
  months,
  months_name
)

Arguments

hpc

Character string or NA. Indicates High Performance Computing mode:

  • NA: Standard processing mode

  • "array": HPC array job mode (requires file parameter)

  • "parallel": HPC parallel mode

file

Character string or NA. Specific file to process when hpc = "array". Not used in other modes.

indir

Character string. Directory containing merged NetCDF files to be time-sliced. Files should be continuous time series created by htr_merge_files().

tempdir

Character string. Directory for temporary files during processing. Used to store intermediate files after month selection before seasonal averaging.

outdir

Character string. Directory where time-sliced files will be saved.

months

Character vector. Month numbers defining the season in two-digit format (e.g., c("12", "01", "02") for DJF, c("06", "07", "08") for JJA). Must be zero-padded (e.g., "01" not "1").

months_name

Character string. Descriptive name for the season that will be added to output filenames (e.g., "DJF", "JJA", "monsoon", "dry-season").

Value

No return value. The function creates seasonal files in the specified output directory with "seasonal" and the season name added to the original filenames (e.g., "merged" becomes "_seasonal_YYYYMMDD-YYYYMMDD_seasonname.nc").

Details

The function creates seasonal climate data through a two-step CDO process:

  1. Month selection: Uses cdo selmon to select only the months that define the season

  2. Seasonal averaging: Uses cdo yearmonmean to calculate yearly means across the selected months

The CDO operations performed are:

cdo selmon,month1,month2,month3 input_file temp_file
cdo yearmonmean temp_file output_file

This approach allows for flexible seasonal definitions (e.g., DJF for winter, JJA for summer, or custom seasons like monsoon periods). The function automatically updates filenames to include "seasonal" and the season name.

Temporary files are used during processing and are stored in the specified temporary directory.

Note

  • Requires CDO (Climate Data Operators) to be installed and accessible from the system PATH

  • Input data should be monthly or daily frequency for meaningful seasonal aggregation

  • Month numbers must be zero-padded two-digit strings ("01", "02", etc.)

  • Temporary files are created during processing but not automatically cleaned up

  • Uses parallel processing when hpc is not set to "array"

  • Ensure sufficient disk space in the temporary directory

References

CDO User Guide: https://code.mpimet.mpg.de/projects/cdo/embedded/cdo.pdf CDO selmon operator: https://code.mpimet.mpg.de/projects/cdo/embedded/cdo.pdf#page=125 CDO yearmonmean operator: https://code.mpimet.mpg.de/projects/cdo/embedded/cdo.pdf#page=192

Examples

if (FALSE) { # \dontrun{
# Create DJF (winter) seasonal data
htr_seasonal_frequency(
  hpc = NA,
  file = NA,
  indir = here("data", "proc", "sliced", "omip", variable),
  tempdir = here("data", "temporary"),
  outdir = here("data", "proc", "seasonal", "omip", variable),
  months = c("12", "01", "02"), # December, January, February
  months_name = "DJF" # Winter season
)

# Create custom monsoon season
htr_seasonal_frequency(
  hpc = NA,
  file = NA,
  indir = here("data", "proc", "sliced", "omip", variable),
  tempdir = here("data", "temporary"),
  outdir = here("data", "proc", "seasonal", "omip", variable),
  months = c("06", "07", "08", "09"), # June through September
  months_name = "monsoon"
)
} # }