Use the CAMS auxiliary data

if you intend to use the data from Copernicus Atmosphere Monitoring Service (CAMS), that we use to get an information on the aerosol type, you will need to download the CAMS data.

CAMS data can be downloaded after a simple registration, but it may take time to download a day of CAMS data. Through agreements with ECMWF or through your countries weather agency, it is possible to get a privileged access, which grants far better performances. To get a better access, it is also possible to download data month per month, instead of day per day. Downloading a month takes almost the same time as downloading a day. But it does not work for real time processing, which needs day per day downloads.

To download and prepare the adequate CAMS data, you may use the camsdownload utility.

Note : camsdownload automatically manages with CAMS versions, switching its requests according to the release dates of versions 46r1, 47r1 and 48r1 (the later starting from MAJA 4.8+)

Step 1: create your CDS account

url: https://ads.atmosphere.copernicus.eu/api/v2
key: uid:api_key

Step 2: call camsdownload

usage: camsdownload  [-h] -d START_DATE -f END_DATE -a
                              ARCHIVE_DIR -w WRITE_DIR [-k] -p
                              {s2,l8,ve,spot} [-e]

optional arguments:
  -h, --help            show this help message and exit

required arguments:
  -d START_DATE, --start_date START_DATE
                        start date, fmt("20171201")
  -f END_DATE, --end_date END_DATE
                        end date, fmt("20171201")
  -a ARCHIVE_DIR, --archive_dir ARCHIVE_DIR
                        Path where the archive DBL files are stored
  -w WRITE_DIR, --write_dir WRITE_DIR
                        Temporary path where the products should be downloaded
  -k, --keep            keep raw netcdf files
  -p {s2,l8,ve,spot}, --platform {s2,l8,ve,spot}
  -e, --extented_time   Retrieve CAMS reanalysis every 3 hours (only for SPOT platform)

Example

~/MAJA/4.8.0/bin/camsdownload -d 20180101 -f 20180102  -w /path/to/my/CAMS_archive -a /path/to/my/tmp/folder

Description of the downloaded CAMS collection

You’ll find one directory per timestep (12 hours), together with its metadata file (same name, with .HDR extension). Each folder contains 3 netCDF files, eg.

CAMS_AOT_20220331UTC120000.nc
CAMS_MR_20220331UTC120000.nc
CAMS_RH_20220331UTC120000.nc
  • CAMS_AOT_* : contains the global Aerosol Optical Tickness of each of the seven aerosol species for the given timestamp
  • CAMS_MR_* : contains the global aerosols mass mixing ratio of each of the seven aerosol species for the given timestamp for each model level (137 levels)
  • CAMS_RH_* : contains the global vertical distribution of the relative humidity for 22 levels

IMPORTANT: it is worth mentioning that one single timestamp of CAMS product take 1.6Go

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