ALCF-DOWNLOAD(1)

NAME
alcf-download - Download model data.

SYNOPSIS
alcf download <type> [login_options] --login
alcf download <type> point: { <lon> <lat> } time: { <start> <end> } [<options>] [--] <output>
alcf download <type> track: <track> [<options>] [--] <output>

DESCRIPTION
This command downloads model data required by the lidar simulator for a given geographical point or ship track. Not all models supported by the other ALCF commands are supported by alcf download - these have to be acquired manually. Before downloading data, you have register an account on Copernicus CDS (ERA5; https://cds.climate.copernicus.eu) or NASA Earthdata (MERRA-2; https://earthdata.nasa.gov) and run alcf download <type> --login. This prompts for credentials interactively. For non-interactive use, use the --overwrite option and credential options (see the login options below). Only geographical subsets necessary to cover the point or track are downloaded.

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

ARGUMENTS

○   type: Model type (see Model types below).

○   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.

○   output: Output directory.

○   login_options: See login options below.

○   options: See Options below.

OPTIONS

--nocache
    Disable server-side caching of requests, when applicable.

--overwrite
    Overwrite existing files.

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).

LOGIN OPTIONS

--overwrite
    Overwrite existing files.

MERRA-2 LOGIN OPTIONS

user: <value>
    Supply non-interactive user instead of prompting.

password: <value>
    Supply non-interactive password instead of prompting.

ERA5 LOGIN OPTIONS

uid: <value>
    Supply non-interactive UID instead of prompting.

key: <value>
    Supply non-interactive API key instead of prompting.

MODEL TYPES

era5
    ERA5.

merra2
    MERRA-2.

FILES
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).

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.

EXAMPLES
Log in to the Copernicus CDS (ERA5) service:

    alcf download era5 --login

Download ERA5 data at 45 S, 170 E between 1 and 2 January 2020 and store the output in the directory era5.

    alcf download era5 point: { -45.0 170.0 } time: { 2020-01-01 2020-01-02 } era5

Log in to the NASA Earthdata (MERRA-2) service:

    alcf download merra2 --login

Download MERRA-2 data for a ship track track.nc and store the output in the directory merra2.

    alcf download merra2 track: track.nc merra2

COPYRIGHT
Copyright © 2019–2024 Peter Kuma, Adrian J. McDonald, Olaf Morgenstern, Richard Querel, Israel Silber and Connor J. Flynn.

BUG REPORTING
Report bugs to Peter Kuma (peter@peterkuma.net).

SEE ALSO
alcf(1), alcf-auto(1), alcf-calibrate(1), alcf-compare(1), alcf-convert(1), alcf-lidar(1), alcf-model(1), alcf-plot(1), alcf-simulate(1), alcf-stats(1)