Data Quality Assessment Scope
Processing levels
Under each of the data release directories, the netcdf files are organised by processing levels (L3, L4, L5 and L6):
- L3 (Level 3) processing applies a range of quality assurance/quality control measures (QA/QC) to the L1 data. The variable names are mapped to the standard variable names (CF 1.8) as part of this step. The L3 netCDF file is then the starting point for all further processing stages.
- L4 (Level 4) processing fills gaps in the radiation, meteorological and soil quantities utilising AWS (automated weather station), ACCESS-G (Australian Community Climate and Earth-System Simulator) and ERA5 (the fifth generation ECMWF atmospheric reanalysis of the global climate).
- L5 (Level 5) processing fills gaps in the flux data employing the artificial neural network SOLO (self-organising linear output map).
- L6 (Level 6) processing partitions the gap-filled NEE into GPP and ER.
Each processing level has two sub-folders ‘default’ and ‘site_pi’:
- default: contains files processed using PyFluxPro
- site_pi: contains files processed by the principal investigators of the site.
If the data quality is poor, the data is filled from alternative sources. Filled data can be identified by the Quality Controls flags in the dataset. Quality control checks include:
- range checks for plausible limits
- spike detection
- dependency on other variables
- manual rejection of date ranges
Specific checks applied to the sonic and IRGA data include rejection of points based on the sonic and IRGA diagnostic values and on either automatic gain control (AGC) or CO
2 and H
2O signal strength, depending upon the configuration of the IRGA.
Calperum Chowilla Flux Tower was established in 2010, and is currently active. The processed data release is currently ongoing, biannually.