I process the eddy covariance data (CH4) using EddyPro. The system composed of LI-7700 and LI-7500. In the full output file, the ch4_flux = un_ch4_flux x ch4_scf. I wish to know,
i) the un_ch4_flux is after WPL correction?
ii) Spectral correction factor is compute from the raw data, before WPL correction?
spectral correction factors are calculated in different ways, depending on the chosen method. In any case, for open-path fluxes, spectral corrections are applied to uncorrected fluxes before adding the WPL terms. This means that in no circumstances you should find that ch4_flux = un_ch4_flux * ch4_scf. Unless, of course: (1) you explicitly de-select the calculation of the WPL terms in EddyPro; (2) data for calculating the WPL terms is missing; or (3) the WPL term is negligible.
In order to understand what’s going on in your case, we would need to look at sample data. Can you please share with us (either here or by email to email@example.com):
1. Two sample raw data files
2. The corresponding metadata file
3. The .eddypro file you created with EddyPro
4. Any additional files you used (such as biomet file, dynamic metadata, etc.).
5. The full output file you obtained, which shows the problem.