Photo: Hanneke Luijting

Data access

Model output is openly available from our thredds server:

Each file is accessible via different protocols, e.g. OPeNDAP, WMS, or direct HTTP download. Files are stored as netCDF-files. Metadata from files are readily accessed using e.g. ncdump, and data may be visualized with ncview. NetCDF is supported in a wide range of programming environments, e.g. Python, Matlab, R, java and several others several others. For a powerful command-line software for subsetting and data extraction, MET Norway recommends fimex.

There are a range of NetCDF files produced each model run, available 3h-3h30min after model initialization time:

  • arome_arctic_extracted_*.nc - Extract of raw model data. Contains variables for surface and pressure levels in the vertical.
  • arome_arctic_full_*.nc - Full model data. Variables for surface and 65 model levels in the vertical.
  • arome_arctic_pp_*.nc - Post processed model data. A selection of surface variables which are post processed after finished model run, see description below. These are the basis for location forecasts at api.met.no and Yr.no.
  • arome_arctic_ppalgs_*.nc - Files for ducting, icing, contrails. See https://gitlab.met.no/mapp/ppalgs
  • arome_arctic_sfx_*.nc - Raw model output from the surface module (SURFEX) in the AROME-Arctic model.
  • arome_arctic_vc_*.nc - Raw model output of vertical profiles and cross sections of the atmosphere from a preselected set of locations.

Post processing variables  

Precipitation:  The precipitation forecasts are post processed using a neighbourhood method. The current neighbourhood size is 37.5*37.5 km. Low, middle and high estimates of precipitation area given by the 20%, 50% and 80% percentiles respectively. 

Cloud area fraction: The cloud area fractions are post-processed using the median value of a neighbourhood area of 37.5*37.5 km.

Air temperature: 2m air temperature forecasts are corrected with a Kalman filter at observing stations. The corrections are interpolated horizontally by kriging, using weights which decrease with increasing distance from the observing stations, both horizontally and vertically.

Strike probability: Probability of Polar Low occurring within the 42 first hours. Calculated by tracking vorticity maxima in the 925 hPa wind field.