The CMEMS GlobColour chlorophyll <i>a</i> product based on satellite observation: multi-sensor merging and flagging strategies

Garnesson, Philippe; Mangin, Antoine; Fanton d'Andon, Odile; Demaria, Julien; Bretagnon, Marine

doi:https://doi.org/10.5194/os-15-819-2019

Articles | Volume 15, issue 3

https://doi.org/10.5194/os-15-819-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

The Copernicus Marine Environment Monitoring Service (CMEMS):...

https://doi.org/10.5194/os-15-819-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 15, issue 3

Research article

|

24 Jun 2019

Research article |

| 24 Jun 2019

The CMEMS GlobColour chlorophyll a product based on satellite observation: multi-sensor merging and flagging strategies

Philippe Garnesson, Antoine Mangin, Odile Fanton d'Andon, Julien Demaria, and Marine Bretagnon

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Final revised paper (published on 24 Jun 2019)
Preprint (discussion started on 02 Jan 2019)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review of 'The CMEMS GlobColour Chlorophyll-a Product Based on Satellite Observation'', Anonymous Referee #1, 24 Jan 2019
- AC1: 'Response to your comments', Philippe Garnesson, 05 Apr 2019
RC2: 'Review of ‘The CMEMS GlobColour Chlorophyll-a Product Based on Satellite Observation’ by Granesson et al.', Emmanuel Boss, 12 Feb 2019
- AC2: 'Response to your comments.', Philippe Garnesson, 05 Apr 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Philippe Garnesson on behalf of the Authors (05 Apr 2019) Manuscript

ED: Referee Nomination & Report Request started (22 Apr 2019) by Pierre-Yves Le Traon

RR by Emmanuel Boss (27 Apr 2019)

RR by Anonymous Referee #1 (09 May 2019)

Suggestions for revision or reasons for rejection

There has been many improvments in the manuscript but it has to be revised again and the text has to be carefully checked for an easier reading.

My major remarks concern :

1) The flagging approach (developed in 2.2)

Please, don’t say that a specific flagging is directly associated with OC5. « One specificity of the OC5 algorithm is to use its own strategy to flag the data » You can say that OC5 is more robust than other usual algorithms and that, developed for coastal waters particularly flagged for diverse reasons, it performs correctly with a lower level of flagging. For instance, there is no OC5 Sun Zenithal Angle (SZA) limit at 78° in Gohin et al. (2002). It is your choice and there is no problem on that but tell the reader clearly it is your strategy to adapt the agencies flags to provide a better spatial and temporal coverage for GlobColour. It is for the user’s benefit.

2) The algorithms for retrieving Chl-a in GlobColour.

You write in the introduction that the GlobColour chlorophyll-a product relies on a combination of different algorithms :
-CI for oligotrophic waters
-OC3 and OC4 for mesotrophic waters
-OC5 for complex water.

However later in the text (from 2.1) you say that a new approach has been chosen at the beginning of 2018, proposing a Chl-a retrieval from CI+OC5.

The listing of the algorithms, in relation to water types, is instructive and can be kept in the introduction as basic algorithms that you used in GlobColour but could you explain that for simplification you decided to combine only two algorithms CI and OC5. It will be more consistent with 2.1 and the rest of the article.

By the way, OC5 is not more empirical than the others (line 20 page 2).

Many specific remarks on the text and the english (although I am not a native english speaker).

- You introduced RRS three times. The first time is line 15 page 3. Could you change « merged Reflectance (RRS) » for merged Reflectance of Remote-Sensing (RRS) and avoid (RRS) in other occurrences.

-CI (Hu, 2012). Please keep CI but avoid CI/HUE (line 25 page 2), CI-Hue (line 15, page 6).

Also always use OC-CCI instead of CCI alone (Figure 8, 9, 11), or worst CI (legend of Figure 10).

Check also the rule for Figures in Ocean Science or keep to a rule when mentioning figures. If you use Figure, write for example « on Figure 6 »

Some remarks on the english

Dependent on, not « of », several times in the text.
Line 20 in the abstract « and uses a more constraints flagging approach »

Page 4 line 9 : to be applied

Page 5 line 10 : is still suffering
« line 25 : demonstrates

Page 5 line 10 : is still suffering
31 : doesn’t correspond to

Page 6 line 12 ; merged reflectance
20 : that can raise to …

Page 7 line 4 : applies
29 : is applied

Many other terms to check in the manuscript.

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ED: Publish subject to minor revisions (review by editor) (09 May 2019) by Pierre-Yves Le Traon

AR by Philippe Garnesson on behalf of the Authors (20 May 2019) Author's response Manuscript

ED: Publish as is (21 May 2019) by Pierre-Yves Le Traon

AR by Philippe Garnesson on behalf of the Authors (22 May 2019) Manuscript

Short summary

This paper concerns the GlobColour chlorophyll α products disseminated by the Copernicus Marine Environmental Monitoring Service (CMEMS). The strategies for merging and flagging remote-sensing data are discussed. Results are illustrated by comparing the CMEMS GlobColour products provided by ACRI-ST with the OC-CCI/C3S products. This highlights the capability of GlobColour to obtain a better spatial coverage and to ingest the OLCI data in complement with SeaWiFS, MERIS, MODIS and VIIRS sensors.