(Latex text formatting)
\noindent{\bf General comments}\\
1. Does the paper address relevant scientific questions within the scope of HESS?\\
I fully agree to Referee #1 of the first stage review of the manuscript:\\
"The authors present a method for the derivation of a global crop calendar based on a combination of census and Earth Observation data. Global crop calendars provide important information for the description of land surface processes not only in agronomical but also in hydrological and climatological context. The presented paper thus well meets the scope of the HESS journal."\\
2. Does the paper present novel concepts, ideas, tools, or data?\\
The idea to use NDVI is not new in itself, but the idea to generate a global crop calendar with the help of remote sensing with some sort of validation, is very exciting.
3. Are substantial conclusions reached?\\
Yes, although some more discussion about spatial resolution of SACRA vs. dominant crops in crop calendars of administrative units would be helpfull (see specific comments).
4. Are the scientific methods and assumptions valid and clearly outlined?\\
Compared to the first version of the manuscript at HESSD, the manuscript has considerably improved and is now in principle acceptable with respect to this point, besides minor issues (see specific comments).
5. Are the results sufficient to support the interpretations and conclusions?\\
To my view, some conclusions should be revised (see specific comments).
6. Is the description of experiments and calculations sufficiently complete and precise to allow their reproduction by fellow scientists (traceability of results)?\\
Compared to the first version of the manuscript at HESSD, the manuscript has considerably improved and is now in principle acceptable with respect to this point, besides minor issues (see specific comments).
7. Do the authors give proper credit to related work and clearly indicate their own new/original contribution?\\
Yes.
8. Does the title clearly reflect the contents of the paper?\\
I cannot suggest a better meaning. A perhaps even shorter wording could be: "SACRA － A method to estimate global high-resolution crop calendars from satellite-sensed NDVI"
9. Does the abstract provide a concise and complete summary?\\
It is strange that the finer spatial resolution of SACRA is mentioned in the abstract, but in the text most interpretation, e.g. Fig. A4 is made on aggregated data, or Fig. 11 by using dominant crop classes.\\
To my feeling, some words should be added about how dominant crop classes are extracted or used, especially in view of discrepancies of crop calendars (see specific comments).
10. Is the overall presentation well structured and clear?\\
Compared to the first version of the manuscript at HESSD, the manuscript has considerably improved.\\
See specific comments.
11. Is the language fluent and precise?\\
Compared to the first version of the manuscript at HESSD, the manuscript has considerably improved.\\
However, in new parts of the manuscript, some wording should be improved for more clarity (see specific comments).
12. Are mathematical formulae, symbols, abbreviations, and units correctly defined and used?\\
One equations misses full explanation of subscripts (see specific comments).
13. Should any parts of the paper (text, formulae, figures, tables) be clarified, reduced, combined, or eliminated?\\
See specific comments.
14. Are the number and quality of references appropriate?\\
Yes.
15. Is the amount and quality of supplementary material appropriate?\\
No supplementary material is currently provided with the manuscript. Data set is planned to be available in the future via a website.\\
\\
\noindent{\bf Specific comments}\\
\\
1) It remains a little bit unclear, why SACRA crop calendars are adjusted to meet length of MIRCA2000 crop calendar of the dominant crop
(sections 2.3 and 2.4), given the fact that ONE crop is chosen for an administrative unit out of possible 6 (Table 5),
from which possibly at least one might have similar maximum monthly crop area or even another subcrop in MIRCA 2000
(as e.g. for irrigated wheat in India Uttar Pradesh with two identical areas with different cropping periods,
see MIRCA documentation Table I-211, FHP 09 Appendix I page I-226).
This follows question of Referee# 2 "In the case where two crops with nearly identical area in MIRCA2000 in the crop calendar,
to what extent would the selection of the dominant crop influence the validity?"
This would add to the discussion about the methodological reasons for discrepancies in crop calendars between SACRA, W12 and MIRCA2000.
2) You did not define cropping intensity (P7L8) while using it in Table 2, Figure 5 etc. It is crucial for the understanding.\\
Also, you should mention for/in Fig. 5 that Zabel et al. 2014 are mentioning potential = maximal cropping intensity.
P7L18:\\
"no remarkable inter-annual variability" - I think for China and Kenya in November and December, there are differences between coloured averages.\\
Fig. 6 & P7L29:\\
"double cropping" - I suspect that in Kansas and Spain these are other crops than the dominant crop\\
P7L30-31:\\
"Zabel et al. ... underestimate cropping intensity" & "bimodal" - I suspect that the second peak in Kenya is another crop than Maize.\\
P8L3::\\
"The nearly constant NDVI is characteristic of a tropical forest" - I suspect that in Brazil Rio Grande do Sul you somehow mistakenly
defined rice as the dominant group (wherase it should be maize),
as in the calibration grids maize and soybeans are pure grids, crops which also have largest harvested area (rainfed and irrigated, respectively)
and (probably) also maximum monthly growing area in MIRCA2000 (see MIRCA documentation Table I-73, FHP 09 Appendix I page I-88)\\
\\
Perhaps it would help to introduce two additional columns in Table 3 (P24) with MIRCA number of cropping periods or some
simplified cropping intensity (CI) for rainfed (RF) and irrigated (IR) crop class,
calculated as the sum to the crop-class specific harvested area divided by the largest harvested area of the (dominant) crop.\\
This CI would read (IR & RF):\\
Brazil:\\
rice 1 >1\\
maize 1 1\\
soybeans 1 1\\
China:\\
wheat 1 1\\
India:\\
wheat 2 >1\\
Kenya:\\
maize 1 1\\
Spain:\\
barley 1 1\\
wheat 1 1\\
P4L28:\\
Please write "nearest 30 arc-min grid". It may be worth discussing the effect of using the 0.5 degree resolution.\\
P5L1-2:\\
So what is the difference between temperate-wheat / snow-wheat vs. spring-wheat / winter-wheat?\\
P7L1:\\
Please delete "common", as maximum nNDVI is 1. But mention that NDVIbas is different for nNDVI 1, or 2.
P7L6:\\
"16 crop types (Table 1b)" : Perhaps Table 2, P23?
P7L9:\\
Please insert "The location of six ..."\\
\\Section 2.3\\
P8L8:\\
"First estimation..." would be inline with Figure 1.\\
You describe crop calendars for temperate crops and snow-wheat.\\
What about rice and multi-cropping?\\
\\Section 3.1\\
P10L17:\\
Eq.8 & 9: What are "F" and "F-1"?
P11L9-10:\\
"no-crop calendar" - Please explain how you could the derive NDVI-Crop!\\
\\Section 3.2\\
P11L15:\\
"Averaged _adjusted_? crop calendars over MIRCA? administrative units.
P11L17:\\
"Major cultivation season" - Please explain how you defined major vs. second (first, area, etc.).\\
P11L19-20:\\
"only single cropping grids" - Please explain how this possibly influences the result.
P12L10-11:\\
Do you mean "GLCC AND Ecoclimap" (i.e. alternative or?) or "GLCC + Ecoclimap" forest land cover (sum of both possible pixels)\\
P12L14ff:\\
Here winter wheat is mentioned, while you speak also of snow-wheat. This wording should be homogenized.\\
P12L21 (and other occasions in the text):\\
Please mention code of unit (as in Table 5) in text (and in caption of Figure 11), to be much faster readable.\\
P13L12-13:\\
Why should finer resolution help to reduce uncertainty in NDVI?\\
I suspect that a possible reason major discrepancy in crop calendars for interpretation is the selection of one dominant crop class (see before).\\
\\Appendix A\\
P17L10:\\
Please insert "from NDVI-Pure" for clarification of source.\\
P17L16ff:\\
Please insert "sowing (OR harvesting)"
P17L18:\\
Please insert "1st (OR end)"
\\Table 3\\
P24:\\
Please mention that assigned code is SACRA code (and not MIRCA code).
\\Figure. 9\\
P36L5:\\
Please insert an explanation of the square on the right side of the figure (-2), and perhaps an explanation of the major cultivation season.\\
Didn't you only use single cropping grids (also in Figure A3)?
\\Figure. A1\\
P39L5:\\
Please specify "nNDVIsw or nNDVIhv" in order to be clear to refer to either parameter and not the ratio of both.\\
\noindent{\bf Technical corrections}\\
See previous section "Specific comments". |
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