Review on the Role of GNSS Meteorology in Monitoring Water Vapor for Atmospheric Physics
Round 1
Reviewer 1 Report
The manuscript has been updated from its original version. Therefore, it can be published after a few minor edits.
Specific comments are in the pdf files.
Comments for author File: 
Comments.pdf
Author Response
Dear Reviewer,
The authors thank your comments. We have followed all of your suggestions. You can find the new version with highlighted changes in the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
I read the paper with the modifications made by the authors and without a doubt, the paper has improved a lot and now deserves to be published. The only thing I can point out is that the paper must be revised by an English native.
Author Response
Dear Reviewer,
Thank you for your suggestion. We have revised the paper with the help of an English native. Please find attached the new version of the manuscript with highlighted changes.
Author Response File: Author Response.pdf
Reviewer 3 Report
The work has improved and it can now be publishedAuthor Response
Dear Reviewer,
Thank you very much. We have still improved the manuscript following the other reviewers' comments.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
This paper is reviewed the recent GPS water vapor estimation techniques and relevant studies. I think the manuscript basically poor, and some points should be reorganized especially.
- section 3.2
This section describes the validation of numerical weather models precipitable water using GPS-PWV. Especially for the forecasting model data and reanalysis data, the GPS-PWV is generally assimilated into the model. As you know, GPS-PWV is the gathered to GTS system of WMO as one of the routine meteorological data. I feel it is weird for "validation", and this section should be reorganized in more detail.
- bias correction of radiosonde by GNSS
It has well known that the direct observational system radiosonde has a systematic bias in humidity or temperature sensors. These biases are always bothering meteorologist. In the GRUAN community (https://www.gruan.org/), they are using GPS-PWV value as a reference for radiosonde. I feel it must be added to the review paper, such as a GPS water vapor observation.
Overall, the citations are less and not enough. It is better to be clear the period (ex. recent decade, etc.).
Reviewer 2 Report
The manuscript "Review on the role of GPS/GNSS meteorology in monitoring atmospheric water vapor for atmospheric physics" is an interesting review of the contribution of GPS/GNSS to atmospheric studies.
It seems to me that it reviews the main different aspects.
As a general comment, perhaps it would be useful to see some pictures of the most representative results of the different works, in addition to the tables and numbers presented in the text.
Regarding Tables 1 and 2, they should be wider, in order to have the largest characters. It would probably be better in landscape format, even across multiple pages.
In the caption of Figure 1, a brief description of the different symbols may be useful.
There are some papers that I didn't see in the reference list. These are just suggestions, in case they can add valuable information to the discussion.
For example, in paragraph 2.3 Balidakis et al could also help in discussing the impact of troposphere parametrization on IWV trends.
, , , , , , & (2018). Estimating integrated water vapor trends from VLBI, GPS, and numerical weather models: Sensitivity to tropospheric parameterization. Journal of Geophysical Research: Atmospheres, 123, 6356– 6372. https://doi.org/10.1029/2017JD028049
Regarding the comparison and validation using GPS, satellites and reanalysis data there are also these papers:
Vey et al 2010
Alraddawi et al 2018
Zhang et al 2018.
Vey, S.; Dietrich, R.; Rülke, A.; Fritsche, M.; Steigenberger, P.; Rothacher, M. Validation of precipitable water vapor within the NCEP/DOE reanalysis using global GPS observations from one decade. J. Clim. 2010, 23, 1675–1695. DOI: https://doi.org/10.1175/2009JCLI2787.1
Alraddawi, D., Sarkissian, A., Keckhut, P., Bock, O., Noël, S., Bekki, S., Irbah, A., Meftah, M., and Claud, C.: Comparison of total water vapour content in the Arctic derived from GNSS, AIRS, MODIS and SCIAMACHY, Atmos. Meas. Tech., 11, 2949–2965, https://doi.org/10.5194/amt-11-2949-2018, 2018.Zhang, F.; Barriot, J.-P.; Xu, G.; Yeh, T.-K. Metrology Assessment of the Accuracy of Precipitable Water Vapor Estimates from GPS Data Acquisition in Tropical Areas: The Tahiti Case. Remote Sens. 2018, 10, 758. https://doi.org/10.3390/rs10050758
As for studies on a global scale, there are also other papers, in addition to those proposed:
Van Malderen et al 2014
Chen and Liu 2016
Wang et al 2016
Van Malderen, R., Brenot, H., Pottiaux, E., Beirle, S., Hermans, C., De Mazière, M., Wagner, T., De Backer, H., and Bruyninx, C.: A multi-site intercomparison of integrated water vapour observations for climate change analysis, Atmos. Meas. Tech., 7, 2487–2512, https://doi.org/10.5194/amt-7-2487-2014, 2014.
, and (2016), Global water vapor variability and trend from the latest 36 year (1979 to 2014) data of ECMWF and NCEP reanalyses, radiosonde, GPS, and microwave satellite, J. Geophys. Res. Atmos., 121, 11,442– 11,462, doi:10.1002/2016JD024917.
Wang, J., Dai, A., & Mears, C. (2016). Global Water Vapor Trend from 1988 to 2011 and Its Diurnal Asymmetry Based on GPS, Radiosonde, and Microwave Satellite Measurements, Journal of Climate, 29(14), 5205-5222. DOI: https://doi.org/10.1175/JCLI-D-15-0485.1
I am sure that there will still be other interesting published papers because the topic is of great interest to the scientific community, even if I understand that one must make a choice and insert only the most significant ones.
Reviewer 3 Report
The authors have promised to provide a comprehensive review on the methods to retrieve atmospheric water vapor from GPS/GNSS. A review paper on this issue will definitely be very useful, and the readers will definitely appreciate this. I started reading this manuscript with great interest. Overall structure of this paper is good although a major revision needed before it becomes publishable.
Since this is a review paper, the authors should present critical synthesis of the literature on this topic rather than just describing which author did what. Readers may want to know the agreement and disagreement on the methods, results and the accuracy of the studies that has been done so far in this field, which could have been discussed in this paper with an organized fashion (using a framework of assessing the accuracy of the methods). With that, the authors may want to rewrite the manuscript. The whole manuscript revolves around a style such as “XYZ et al., compared/proposed /described/considered …. “. The readers may not find this very interesting. Also, in the most cases the chain of thought does not remain connected. For example, in line 130 – 136, what is the role of radiosonde here? Which network was used to optimize voxel definition (GPS or Radiosonde)? What do we learn from figure 2? In line 135, the authors mentioned “Haji-Aghajany-Amerian showed a method”. What is that method? In line 136 and 129 RMSEs were described using different units. Therefore, I would suggest that author synthesize and present the review in a clear manner so that the readers enjoy reading. Authors should also focus on figures, so that they meet publication quality standard. For example, Figure 1 has North America continent twice. The symbols are classified without any legitimate reason. The table are very hard to read.
Reviewer 4 Report
Review of the paper "Review on the role of GPS/GNSS meteorology in monitoring atmospheric water vapor for atmospheric physics".
This paper intends to present a review of the methodologies to retrieve atmospheric water vapor content using GNSS. The first problem I notice is the use of the terms GPS and GNSS. We know that the first and most well-known system was GPS, but authors should adopt the terms GNSS throughout the text and make the correct reference to the importance of GPS at the beginner. The term GPS/GNSS makes no sense given that GNSS includes GPS and only confuses the reader.
Although it is a review, this work is not well structured; the order of the sections does not make any sense, nor do we understand what is really being treated in this paper.
I believe that this paper has a structural problem. The authors begin by saying that this paper is a review. However, section 2 (2.1) is about GNSS tomography. This is one of the last GNSS applications (last ten years); section 2.2 is about converting form delay into precipitable water. Section 2.3 talks about analyzing the error?. This structure is meaningless. After reading this paper I was more confused than elucidated.
A lot of references are missing in several sections.
Figure 1 was obtained from the IGS website and is a rough copy/paste. At least an indication about the color and symbol shapes is necessary. The sentence "Color and shape are related to the last data available date" not enough.
Line 92, GeoForschungsZentrum ? better the term “GFZ-Potsdam”
The figures do not support the content of this paper.
Section 4 is divided by continents/countries. It does not make any sense; it should be summarized only in a table (2). I also can't entirely agree with this table because several studies are missing.
I understand the work that this paper gave to the authors. However, it is poorly structured; in almost all sections, the authors limit themselves to transposing conclusions from the references. Without a restructuring of it, my recommendation is to reject its publication.
Reviewer 5 Report
Remotesensing-1094838:
Review on the role of GPS/GNSS meteorology in monitoring atmospheric water vapor for atmospheric physics
- Vaquero-Martinez and M. Anton
The paper presents a review of studies published using GPS/GNSS datasets. The manuscript is generally well written, clear, and it certainly has its merits in summarizing a large number of studies on diverse topics. The manuscript covers 4 major topics and subtopics:
- GPS/GNSS Methodologies (tomography, conversion of delay to wv, error analysis, combination with other measurements)
- Inter-comparisons with other techniques (validation, Validations of NWP with GPS/GNSS water vapor as reference, Validation of satellite measurements with GPS/GNSS as reference, General intercomparison)
- Spatio-temporal analysis (Asia, Europe, Africa, America, Antarctic, Global)
- Impact of water vapor variability on meteorology and climate (Assimilation, Circulation, Radiative transfer, Other)
Notwithstanding the vast amount of work accomplished by the authors, at the end of the paper the reader is left with many disconnected pieces of information, sometime conflicting, but not much of an overall idea of where the field is going and what are the challenges ahead.
My recommendation would be to re-think the overall concept of the paper from a compilation of work done, to a work of synthesis that uses the bibliographical research already presented in addition to the author’s extensive knowledge of the field. It would be very useful, at the end of each section, to identify and summarize what are the major issues still open, what can be done to address these issues both on the experimental and computational ends, and what are the impediments to go forward.
Just to provide one example Table 1 shows a wide range of biases, RMSE and correlations and is not easy to know what to make out of it. What are these results telling us about the GPS measurements? In general what is the best use for these measurements and what can be done to understand them better.
It would also be interesting to know the author’s recommendations for future research on each topic. This part would be important because it could provide other researchers in the field with a motivation for designing future experiments.
