Automatic Lidar and Ceilometer

Command line interface

alcf-model – Extract model data at a point or along a track.


alcf model <type> point: { <lon> <lat> } time: { <start> <end> } [options] [--] <input> <output>

alcf model <type> track: <track> [options] [--] <input> <output>


Arguments following -- are treated as literal strings. Use this delimiter if the input or output file names might otherwise be interpreted as non-strings, e.g. purely numerical file names.


  • type: Input data type (see Types below).
  • input: Input directory.
  • output: Output directory.
  • lon: Point longitude (degrees East).
  • lat: Point latitutde (degrees North).
  • start: Start time (see Time format below).
  • end: End time (see Time format below).
  • track: <file>, track: { <file>... }: One or more track NetCDF files (see Files below). If multiple files are supplied and time_bnds is not present in the files, they are assumed to be multiple segments of a discontinous track unless the last and first time of adjacent tracks are the same.
  • options: See Options below.


  • njobs: <n>: Number of parallel jobs. Default: number of CPU cores capped to 16.
  • -r: Process the input directory recursively.
  • --track_lon_180: Expect track longitude between -180 and 180 degrees. This option is no longer needed as the conversion is automatically. [deprecated]
  • override_year: <year>: Override year in the track. Use if comparing observations with a model statistically and the model output does not have a corresponding year available. The observation time is converted to the same time relative to the start of the year in the specified year. Note that if the original year is a leap year and the override year is not, as a consequence of the above 31 December is mapped to 1 January. The output retains the original year as in the track, even though the model data come from the override year. Default: none.
  • track_gap: <interval>: If the interval is not 0, a track file is supplied, the time_bnds variable is not defined in the file and any two adjacent points are separated by more than the specified time interval (seconds), then a gap is assumed to be present between the two data points, instead of interpolating location between the two points. Default: 21600 (6 hours).


  • amps: Antarctic Mesoscale Prediction System (AMPS).
  • era5: ERA5.
  • icon: ICON.
  • icon_intake_healpix: ICON through Intake-ESM on HEALPix grid.
  • jra55: JRA-55.
  • merra2: Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2).
  • nzcsm: New Zealand Convection Scale Model (NZCSM).
  • nzesm: New Zealand Earth System Model (NZESM). [Experimental]
  • um: UK Met Office Unified Model (UM).

Time format

YYYY-MM-DD[THH:MM[:SS]], where YYYY is year, MM is month, DD is day, HH is hour, MM is minute, SS is second. Example: 2000-01-01T00:00:00.


The track file is a NetCDF file containing 1D variables lon, lat, time, and optionally time_bnds. time and time_bnds are time in format conforming with the CF Conventions (has a valid units attribute and optional calendar attribute), lon is longitude between 0 and 360 degrees and lat is latitude between -90 and 90 degrees. If time_bnds is provided, discontinous track segments can be specified if adjacent time bounds are not coincident. The variables lon, lat and time have a single dimension time. The variable time_bnds has dimensions (time, bnds).


Extract MERRA-2 model data in M2I3NVASM.5.12.4 at 45 S, 170 E between 1 and 2 January 2020 and store the output in the directory alcf_merra2_model.

alcf model merra2 point: { 170.0 -45.0 } time: { 2020-01-01 2020-01-02 } M2I3NVASM.5.12.4 alcf_merra2_model