Satellite and In Situ Observations for Advancing Global Earth Surface Modelling: A Review

Round 1

Reviewer 1 Report

The manuscript is a thorough review of the links between observations and models of the surface of Earth. The various sections cover the essential aspects of the topics discussed and present some instructive ideas without excessive details. The authors achieved a good balance among the many items addressed in their article, and I am quite convinced that many readers will appreciate the collection of facts presented here in one place. So I can only suggest the following, minor changes.

Lines 53 and 54: I do not see how a likely event can be a fact. If the authors want to make the statement that extreme weather is now more frequent because of global warming, they should quote an article from the scientific literature with the details.

Lines 131 - 133: AMSU-A on Aqua has degraded performance, because its channels 23.8, 31.4, 52.8, 53.596± 0.115 and 54.94 GHz are not functional. AMSRE is inactive since 04 Oct 2011. So the description given in these lines is euphemistic. 

Lines 138 - 140: The last section of the review paper is "Summary and Outlook". I did not find the word "MODIS" in there.

Line 150: The last time the word "LANDSAT" appears in the text is in section 4.1.2, but this is not the section before last. 

Figure 1:This figure should be larger, and it should be referred to somewhere in the text.

Table 1: should be referred to in the text.

Figure 2: The numbers giving the temperature as a function of colour are too small. 

Line 249: FY-2F is at 112 degrees E and MTSAT-2 is inactive since 10 Mar 2017. 

Table 2: The operating longitudes are not correct in several cases: Meteosat-3 (ADC), for example, is at 50 degrees W, Meteosat-10 is at 9.5 degrees E, FY-2F is at 112 degrees E, etc.

Figure 3: The numbers on the axes of the right panels are too small.

Figure 4: The numbers giving the observation density as a function of colour are too small. 

Line 325: The web address given here does not exist. 

Figure 6: Explain the abbreviations "BSWB" and "GSWP", give the names of all rivers in English (e. g. "Oder" instead of "Odra") for consistency and add a legend for the right panel as well.

Figure 7: is too small, explain the abbreviation "BEVAP".

Figure 9: The title of the x-axis should be "time" instead of "Fraser".

Figure 12: There is a free-floating "-" in the legend.

Line 642: Explain the abbreviation "GOSAT".

Figure 14: Explain the abbreviation "GRACE". It will help the reader if you add coordinates or an overlay of the path of the Parana to the maps. 

Figure 15: Explain the difference between the red points and the blue circles in the right hand panel.

Line 795: "occurring earlier" than what? 

Line 849: What is the significance of writing "5x106" instead of "530"? Or do you want to write 5E6?

Line 923: Explain the abbreviation "CEMS". The web address given here does not exist. 

Line 1022: "[259]" instead of "Large and Caron (2015)"

Figure 22: The coordinates of the maps are too small. 

Figure 23: The explanation of the colour coding of panels (a) - (c) is too small.

Figure 25: The coordinates of the maps are too small.

Line 1208 - 1211: A reference for the water surface area in 1998 and 2008 should be given. If it is the English page of Wikipedia, then I want to call attention to the fact that the German page gives quite different numbers.

Line 1225: There is no section 3.3.4.

Line 1264: There are many satellite pixels with footprints smaller than 20 or larger than 40 km, e. g. with AMSU.

Line 1396: The abbreviation "IFS" should have been explained the first time it appeared, i. e. in line 404.

Lines 1413 and 1416: The web addresses given here do not exist. 

Section 5.5: The authors should elaborate on the statement that coupled data assimilation systems can deal with the inconsistencies among different atmospheric observations. How, for example, do they decide which one of two satellites with systematic differences in their measurements of scene temperature is calibrated correctly?

Abbreviations: Many abbreviations in the text are missing in this list, e. g. "BEVAP", "BSWB", "CEMS", "GOSAT", "GRACE", and "GSWP".

Bibliography: Many entries are incomplete, e. g. 1-3 have the year missing, 14 and 235 have no author name, with 95, 97, and 137 one does not know whether they are articles, books or web pages, 269 has no page number, etc.

Author Response

The authors would like to thank the 3 reviewers for the positive comments and suggestions for improvements. Please find our responses as inserts following the reviewer's request.

Reviewer-1:

The manuscript is a thorough review of the links between observations and models of the surface of Earth. The various sections cover the essential aspects of the topics discussed and present some instructive ideas without excessive details. The authors achieved a good balance among the many items addressed in their article, and I am quite convinced that many readers will appreciate the collection of facts presented here in one place. So I can only suggest the following, minor changes.

We thank the reviewer for the positive comments on the overall balance of the review. We are also grateful for the detailed comments that are addressed as reported below in the text inserts.

Lines 53 and 54: I do not see how a likely event can be a fact. If the authors want to make the statement that extreme weather is now more frequent because of global warming, they should quote an article from the scientific literature with the details.

Reference added. 

Lines 131 - 133: AMSU-A on Aqua has degraded performance, because its channels 23.8, 31.4, 52.8, 53.596± 0.115 and 54.94 GHz are not functional. AMSRE is inactive since 04 Oct 2011. So the description given in these lines is euphemistic. 

Reformulated as follows "About half of the sensors continue transmitting high-quality, in particular from AIRS, CERES, and MODIS, with reduced functionality from AMSU-A channels. AMSR-E became inactive since 2011, with HSB, collected approximately nine months of high quality data but failed in February 2003."

Lines 138 - 140: The last section of the review paper is "Summary and Outlook". I did not find the word "MODIS" in there.

Text changed to reflect the mention to MODIS dataset in section 2.

Line 150: The last time the word "LANDSAT" appears in the text is in section 4.1.2, but this is not the section before last. 

Text changed to reference Section 4.

Figure 1:This figure should be larger, and it should be referred to somewhere in the text.

Figure 1 is made larger to page width and references in the text

Table 1: should be referred to in the text.

Table 1 is now referenced in the text 

Figure 2: The numbers giving the temperature as a function of colour are too small. 

Figure 2 is now larger.

Line 249: FY-2F is at 112 degrees E and MTSAT-2 is inactive since 10 Mar 2017. 

Corrections added in the text and table

Table 2: The operating longitudes are not correct in several cases: Meteosat-3 (ADC), for example, is at 50 degrees W, Meteosat-10 is at 9.5 degrees E, FY-2F is at 112 degrees E, etc.

Corrected in these. It is also aknowledged in the table caption that the position of geostationary satellites is not invariable due to operational management choices.

Figure 3: The numbers on the axes of the right panels are too small.

Figure 3 is now larger.

Figure 4: The numbers giving the observation density as a function of colour are too small. 

Figure 4 is now larger.

Line 325: The web address given here does not exist. 

it is corrected (a "/" was removed)

Figure 6: Explain the abbreviations "BSWB" and "GSWP", give the names of all rivers in English (e. g. "Oder" instead of "Odra") for consistency and add a legend for the right panel as well.

BSWB and GSWP added to the Acronyms, Oder corrected.

Figure 7: is too small, explain the abbreviation "BEVAP".

Figure 7 is now larger. BEVAP is defined and also added to abbreviations.

Figure 9: The title of the x-axis should be "time" instead of "Fraser".

x-axis description added to the legend as follows "Offline simulation results with CTR ECMWF snow scheme (black line – before 2009 revision), and NEW (red line – after 2009 revision) for the 2004–2005 winter season at Fraser forest (a-c) and open (d-f) sites. Snow mass (a,d), snow depth (b,e) and snow density (c,f) are shown, with time on the x-axis (from 1st October 2004 to 1st June 2005). Observations are represented by open blue circles.".

Figure 12: There is a free-floating "-" in the legend.

corrected figure legend by remoting the "-".

Line 642: Explain the abbreviation "GOSAT".

Added to abbreviations.

Figure 14: Explain the abbreviation "GRACE". It will help the reader if you add coordinates or an overlay of the path of the Parana to the maps. 

Added to abbreviations.

Figure 15: Explain the difference between the red points and the blue circles in the right hand panel.

added to the caption.

Line 795: "occurring earlier" than what? 

corrected to "occurring earlier in the year comparing to fixed soil depth simulations".

Line 849: What is the significance of writing "5x106" instead of "530"? Or do you want to write 5E6?

corrected to 5x10^6.

Line 923: Explain the abbreviation "CEMS". The web address given here does not exist. 

Abbreviation added and link corrected.

Line 1022: "[259]" instead of "Large and Caron (2015)"

Corrected.

Figure 22: The coordinates of the maps are too small. 

Figure is larger

Figure 23: The explanation of the colour coding of panels (a) - (c) is too small.

Steffen can you help with this?

Figure 25: The coordinates of the maps are too small.

Figure enlarged

Line 1208 - 1211: A reference for the water surface area in 1998 and 2008 should be given. If it is the English page of Wikipedia, then I want to call attention to the fact that the German page gives quite different numbers.

A reference is added and the text has been revised. UPDATED TEXT:

After massive diversion of water for cotton and rice cultivation in the 1960’s shrinking of water surface area accelerated and in 1998 became 28’990 sq.km (less than a half of its initial size). Due to major recovery program launched in 2001 by Kazakhstan President Nursultan Nazarbayev and supported by the World Bank, Aral Sea water surface area started to stabilise and in 2014 became 7’660 sq.km (almost 10 times less of its initial size).

SOURCE (english): Aral Sea and its sourroudings. Generalization of the SIC ICWC on condition monitoring and situation analysis. Published by UNESCO Office in Uzbekistan and Baktria press. [In Russian]. 2017. ISBN 978-9943-4895-9-2, Link: http://unesdoc.unesco.org/images/0026/002607/260741R.pdf

SOURCE (original): АРАЛЬСКОЕ МОРЕ И ПРИАРАЛЬЕ. Обобщение работ НИЦ МКВК по мониторингу состояния и анализу ситуации. Опубликовано представительством ЮНЕСКО в Узбекистане и Baktria press. 2017. ISBN 978-9943-4895-9-2,  http://unesdoc.unesco.org/images/0026/002607/260741R.pdf

EXTRACT INFORMATION: At pp 19-21 - Table 2.1: Dynamics of water level, surface area and volume changes of the Extended Aral Sea. Surface area evolution: year 1960 = 68.90 thousand sq.km ;  year 1998 = 28.99 thousand sq.km , year 2008 = 11.52 thousand sq.km ; year 2014 = 7.66 thousand sq.km.

Line 1225: There is no section 3.3.4.

Reference removed.

Line 1264: There are many satellite pixels with footprints smaller than 20 or larger than 40 km, e. g. with AMSU.

Changed to "Satellite pixels in the microwave frequency range have footprints of several kilometres typically encompass many surface types".

Line 1396: The abbreviation "IFS" should have been explained the first time it appeared, i. e. in line 404.

Added to abbreviations.

Lines 1413 and 1416: The web addresses given here do not exist. 

Links updated.

Section 5.5: The authors should elaborate on the statement that coupled data assimilation systems can deal with the inconsistencies among different atmospheric observations. How, for example, do they decide which one of two satellites with systematic differences in their measurements of scene temperature is calibrated correctly?

Changed to "Coupled data assimilation systems would address these issues by allowing a consistent handling of these observations across systems, provided systematic differences (e.g. due to calibration) are removed by bias correction schemes, that can be integral part of the data assimilation system" with addition of a reference to Dee et al 2009.

Abbreviations: Many abbreviations in the text are missing in this list, e. g. "BEVAP", "BSWB", "CEMS", "GOSAT", "GRACE", and "GSWP".

All the above have been added to Abbreviations.

Bibliography: Many entries are incomplete, e. g. 1-3 have the year missing, 14 and 235 have no author name, with 95, 97, and 137 one does not know whether they are articles, books or web pages, 269 has no page number, etc.

Corrected entries as signalled.

Reviewer 2 Report

The authors provide an extensive review of satellite-based remote sensing and in-situ data available for earth surface modelling. The emphasis on combining remotely sensed satellite data with in-situ observations to improve model development has been around in the scientific community for a long time, but this paper reviews surface parameters in great depth.  My other comments are as follows:

 

Main comments:

 

1.     The figures provided are of low resolution. The authors should provide high-resolution figures for a clearer depiction of their arguments.

2.     Section 2.2: The Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS) dataset has not been mentioned.

3.     Section 2.7: Cloud contamination in geostationary images for surface retrieved products may require some emphasis too.

4.     Section 2.9: Ocean-based network such as International Comprehensive Ocean-Atmosphere Data Set (ICOADS) is missing.

5.     A table of all the sensors and the surface variables it can measure or infer can be highly useful in this review paper.

6.     The authors do not discuss the major errors or uncertainties governing the various active or passive sensors.

7.     The authors should also discuss future missions that can add to the current fleet of observations that have some limitations.

Author Response

The authors would like to thank the 3 reviewers for the positive comments and suggestions for improvements. Please find our responses as inserts following the reviewer's request.

Reviewer-2

The authors provide an extensive review of satellite-based remote sensing and in-situ data available for earth surface modelling. The emphasis on combining remotely sensed satellite data with in-situ observations to improve model development has been around in the scientific community for a long time, but this paper reviews surface parameters in great depth.  

We thank the reviewer for the comment on the depth of the review paper. The reviewer points out a set of very useful comments for which comments and text revisions are reported as text inserts.

 

My other comments are as follows:

1.     The figures provided are of low resolution. The authors should provide high-resolution figures for a clearer depiction of their arguments.

Figure rendering has been improved by adopting larger size figures with the purpose of improved readability. Some of the figures have been completely re-rendered or re-done.

2.     Section 2.2: The Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS) dataset has not been mentioned.

Reference to AirMOSS field campaign is added via referencing the publication and the web-site https://airmoss.ornl.gov

3.     Section 2.7: Cloud contamination in geostationary images for surface retrieved products may require some emphasis too.

This is a common problem for geostationary and polar orbiting satellites.

4.     Section 2.9: Ocean-based network such as International Comprehensive Ocean-Atmosphere Data Set (ICOADS) is missing.

ICOADS is a data set compilation of Ocean-based networks.

5.     A table of all the sensors and the surface variables it can measure or infer can be highly useful in this review paper.

We do reference the published NASA decadal survey of 2018 or the GCOS reports that do contain this extensive information. 

6.     The authors do not discuss the major errors or uncertainties governing the various active or passive sensors.

Indeed we aknowledge that uncertainty are not sufficiently covered in the paper and would deserve a more ample discussion. This aknowledged both in the introduction and in the conclusions.

7.     The authors should also discuss future missions that can add to the current fleet of observations that have some limitations.

This is beyond the scope of the current review paper and shall be considered in future contributions of the working group.

Reviewer 3 Report

This article is a review of satellite and in situ observations for global earth surface modeling. My main concern is Section 2 (8 pages) only listed some very general information of several satellite products and some in situ networks. The readers could easily find the information elsewhere. This review article may further address some cross comparisons of different products, the uncertainties, the cautions the users need to consider based on some literatures. And if this part is not the focus, may focus on Section 3 – Section 5. Make the Section 2 as concise as possible.

Some specific comments are listed below to help improving the impact of this article: 

1, A simple table could summarize the Section 2 in a clearer way. The table could only include some main features, such as the name of the products, resolutions, available time period, and references or website. And the authors should consider to put the table as supplementary material if they want to include more detail information. I recommend only include the necessary message to make a concise review paper.

2, This is a long review article, list the index of each section and sub sections in front of Section 2 would be very helpful for readers to get the main structure of the article, and get to the part which interest them the most.    

Author Response

The authors would like to thank the 3 reviewers for the positive comments and suggestions for improvements. Please find our responses as inserts following the reviewer's request.

Reviewer-3

This article is a review of satellite and in situ observations for global earth surface modeling. My main concern is Section 2 (8 pages) only listed some very general information of several satellite products and some in situ networks. The readers could easily find the information elsewhere. This review article may further address some cross comparisons of different products, the uncertainties, the cautions the users need to consider based on some literatures. And if this part is not the focus, may focus on Section 3 – Section 5. Make the Section 2 as concise as possible.

The authors would like to support still the usefulness of Section 2. While it is surely information that can be found in a review it serves the purpose of collecting the information in a single place.

Some specific comments are listed below to help improving the impact of this article: 

1, A simple table could summarize the Section 2 in a clearer way. The table could only include some main features, such as the name of the products, resolutions, available time period, and references or website. And the authors should consider to put the table as supplementary material if they want to include more detail information. I recommend only include the necessary message to make a concise review paper.

It is difficult to use a table for summarising a large amount of heterogeneous information. With the transition of models from weather prediction to more complete Earth system prediction the range of Earth surface modelling application is increasing and the key role of observations is a key point that support maintaining the observations sections central to the manuscript and not as supplementary material.

2, This is a long review article, list the index of each section and sub sections in front of Section 2 would be very helpful for readers to get the main structure of the article, and get to the part which interest them the most.    

Indeed a better indexing of the sections is added at the end of introduction.

Round 2

Reviewer 3 Report

This version is fine.