Process NetCDF rasters for a given year

This function processes a directory of NetCDF files by extracting a specified variable (surface level only), cropping/masking to a polygon, and optionally downsampling to a target resolution. It outputs a single combined raster for the year and writes it to a temporary GeoTIFF file.

Usage

process_year(
  year_dir,
  polygon,
  crop,
  mask,
  downsample,
  res,
  variable,
  preliminary
)

Arguments

year_dir: Character. Path to the directory containing .nc files for a single year.
polygon: An sf polygon object. Used for cropping and/or masking rasters.
crop: Logical. If TRUE, crops rasters to the extent of polygon.
mask: Logical. If TRUE, masks rasters to the interior of polygon.
downsample: Logical. If TRUE, resamples rasters to a coarser grid of resolution res.
res: Numeric (length 1 or 2). Target resolution for downsampling (map units of CRS).
variable: Character. Variable name prefix to extract from NetCDF (e.g. "sst"). The function appends "_zlev=0" to match surface data layers.
preliminary: Logical. If TRUE, allows processing of files flagged as preliminary. If FALSE (default), the function will stop if preliminary data are found.

Value

Character. Path to the combined yearly raster written to a temporary GeoTIFF, or NULL if no valid rasters were processed.

Details

The function:

Scans year_dir for .nc files.
Skips or replaces filenames with _preliminary.nc depending on preliminary.
Extracts the specified variable at surface depth (zlev=0).
Applies optional crop/mask/downsample steps.
Combines rasters and writes out a GeoTIFF file in the session temp directory.

Examples

if (FALSE) { # \dontrun{
library(sf)
poly <- st_read("polygon.gpkg")
tif <- process_year("data/1998", poly, crop = TRUE, mask = TRUE,
                    downsample = TRUE, res = 0.1, variable = "sst", preliminary = FALSE)
raster <- terra::rast(tif)
} # }