Welcome to the CAMS43-Aerosol-Alert wiki! This wiki describes briefly how the CAMS43 aerosol alert system works.

The code in this repository will only prepare the data according to the aerocom standard, but not plot it. Met Norway uses for this purpose its self developed so called aerocom-tools which cannot be provided in a public repository because they use external libraries that do not have a GPL compatible license.

The aerocom-tools need a yearly file per variable. The code therefore always prepares a yearly file per used variable and will fill the unused time steps with NaN data. Due to the fact the year change is very hard to test (e.g. the clock cannot be changed in a virtual machine), this code will always fail at the last days of a year in the sense that forecast data from the new year will not be prepared. The download will be done though. Data preparation for the new year will be resumed first January automatically.

System requirements

• multi core reasonably up to date Linux system (Met Norway: 40 cores, 128GB RAM)
• nco >= version 4.7 (earlier versions need small adjustments in the code; --trd switch)
• cdo >= version 1.9 (earlier versions might work as well)
• 32GB RAM
• storage of ~1.7 TB per year (download is ~0.5 TB, unpacked data (for midnight forecast only) is ~0.5 TB, interpolated data is ~0.7 TB). Note that netcdf4 file compression cannot be used since that leads to a 6 times longer file preparation time

Warning: As the system is configured right now it easily creates a system load around 120 during data preparation time. Documentation of how to lower this load will be put in the system description.

general steps to be done

• download forecast data from ECMWF
• unpack (netcdf packing is file specific; see system description for details.
• interpolate to common grid (grid can change within a year; climatology grid might be different)
• create climatology on common grid
• prepare yearly file of all used variables (see system description for details).
• calculate alert

You might want to continue with a more detailed system description.