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Process meteorological and atmospheric data

Source: R/process.R
process_merra2.Rd

The process_merra2() function imports and cleans raw atmospheric, meteorological, and MERRA2-based Fire Weather Index data, returning a single SpatRaster object.

Usage

process_merra2(
  date = c("2018-01-01", "2018-01-10"),
  variable = NULL,
  path = NULL,
  extent = NULL,
  daily_agg = FALSE,
  fun = "mean",
  ...
)

Arguments

date

character(1 or 2). Date (1) or start and end dates (2). Format YYYY-MM-DD (ex. September 1, 2023 = "2023-09-01").

variable

character(1). MERRA2 variable name(s). For daily corrected Fire Weather Index files (collection = "fwi" during download), use one of "DC", "DMC", "FFMC", "ISI", "BUI", or "FWI" (or the full raw layer name).

path

character(1). Directory with downloaded netCDF (.nc4 or .nc) files.

extent

numeric(4) or SpatExtent giving the extent of the raster if NULL (default), the entire raster is loaded

daily_agg

logical(1). If TRUE, aggregate sub-daily layers to daily values using fun. Default FALSE preserves the original sub-daily output. Aggregation groups layers by variable/level and date. Silently ignored for FWI collections, which are already daily.

fun

character(1). Aggregation function passed to terra::tapp() (e.g. "mean", "max", "min", "sum"). Ignored when daily_agg = FALSE.

...

Placeholders.

Value

a SpatRaster object;

Note

Layer names of the returned SpatRaster object contain the variable, pressure level, date, and hour for standard MERRA-2 collections when daily_agg = FALSE (default). When daily_agg = TRUE, layer names contain the variable, pressure level, and date only, and terra::time() is set to midnight UTC of each date. For daily Fire Weather Index files, layer names contain the variable and date only regardless of daily_agg. Pressure level values utilized for layer names are taken directly from raw data and are not edited to retain pressure level information.

Author

Mitchell Manware

Examples

## NOTE: Example is wrapped in `\dontrun{}` as function requires a large
##       amount of data which is not included in the package.
if (FALSE) { # \dontrun{
merra2 <- process_merra2(
  date = c("2024-01-01", "2024-01-10"),
  variable = "CPT",
  path = "./data/inst1_2d_int_Nx"
)
## daily mean CPT
merra2_daily <- process_merra2(
  date = c("2024-01-01", "2024-01-10"),
  variable = "CPT",
  path = "./data/inst1_2d_int_Nx",
  daily_agg = TRUE,
  fun = "mean"
)
} # }