Dear Authors:

Thank you for providing your response to the referee comments. Both referees recommended major revision with re-consideration to your manuscript. They slightly differed in evaluation of scientific significance and quality of your manuscript (fair or good) and agreed in presentation quality (good). I had a similar question with the referees #1 and #2 about the high GPP estimated by the posterior model, and it was interesting that the change in parameter set was responsible for the new result. I agree with your statement “we do not expect to produce a perfect or accurate global GPP estimate”, because it is premature for the present state of science. About the relationship between SIF and GPP, physiological, theoretical, and modeling studies are developing (e.g., Gu et al., in press; Hikosaka and Noda, 2019). Nevertheless, at least in a ‘relative’ sense, the revised manuscript should clarify how the new model was improved in comparison with previous ones. For other specific points, I confirmed that the authors responded properly.

References
Gu, L., Han, J., Wood, J. D., Chang, Y.-Y., and Sun, Y.: Sun-induced Chl fluorescence and its importance for biophysical modeling of photosynthesis based on light reactions, New Phytologist, 10.1111/nph.15796, in press.
Hikosaka, K., and Noda, H. M.: Modeling leaf CO2 assimilation and photosystem II photochemistry from chlorophyll fluorescence and the photochemical reflectance index, Plant, Cell, and Environ., 42, 730–739, 10.1111/pce.13461, 2019.

Dear Authors:

Thank you for submitting the revised manuscript. Your manuscript, to which major revision was recommended by the two reviewers, received no additional comments. I studied your responses with the annotated manuscript and conclude that it was adequately improved from the previous version. In particular, Discussion part was well extended and re-organized, making the advantages and differences of the study clearer. Because application of satellite-derived SIF is an actively growing research area, this model-fusion study may make a substantial contribution. Presentation quality was already good, but I found several technical points that can make it better. For example, x-axis of latitudinal figures (Figs. 4, 5, 10, and 11) lacks a label (i.e. “Latitude (degree)”). Also, please try to use superior letters for the exponents in units in several figures (e.g., W m–2 µm–1 sr–1). Please try to amend them if technically possible.