You can find a detailed explanation of the different methods that you can use to estimate fluxes here.

“Max number of days between samples to interpolate” refers to the maximum number of days between measured chemistry samples above which the chemistry data is considered missing. Missing data is replaced by the average of the month or the year, depending on the time scale of the measurement.

The estimation of fluxes gives two outputs: the file "flux results" and a file called "calcs" where you can see the internal calculations done to estimate fluxes.

When selecting the time period for the estimation of fluxes, we suggest you to include one month before and after the period of interest to allow for a proper interpolation.