Flux data

[khufkens]

• Put data into separate directories on Euler ~/data for each data source (e.g. PLUMBER2, ICOS, Ameriflux, ...)
• Complement site meta info for extended site set and extended years range (as for ingestr::siteinfo_fluxnet2015), specifying data sources in a separate column (e.g. PLUMBER2, ICOS, Ameriflux, ...)
• Write functions to read flux data for each source separately
  (probably, ICOS and Ameriflux work exactly the same way as FLUXNET2015)
• Read all data (daily scale) from extended set and years into an R data frame and write to one big file.

Priority:

• PLUMBER2
• ONEflux (new Ameriflux data)
• fluxnet2015 (should overlap with ONEflux)
• ICOS Drought2018 (will be overlap with FN2015)
• ICOS release 2021-1