A numerical method to improve the spatial interpolation of water vapor from numerical weather models: a case study in South and Central America

Fernández, Laura I.; Meza, Amalia M.; Natali, M. Paula; Bianchi, Clara E.

doi:https://doi.org/10.5194/angeo-37-1181-2019

Articles | Volume 37, issue 6

https://doi.org/10.5194/angeo-37-1181-2019

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

https://doi.org/10.5194/angeo-37-1181-2019

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

Articles | Volume 37, issue 6

Regular paper

|

16 Dec 2019

Regular paper |

| 16 Dec 2019

A numerical method to improve the spatial interpolation of water vapor from numerical weather models: a case study in South and Central America

Laura I. Fernández, Amalia M. Meza, M. Paula Natali, and Clara E. Bianchi

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Final revised paper (published on 16 Dec 2019)
Preprint (discussion started on 06 Mar 2019)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Review of Fernández et al.', Anonymous Referee #1, 14 Mar 2019
- AC1: 'Answers to the comments on “Comparison of GNSS integrated water vapor and NWM reanalysis data over Central and South America”', Laura Isabel Fernandez, 14 Jun 2019
RC2: 'angeo-2019-20 review', Anonymous Referee #2, 01 Apr 2019
- AC2: 'Answers to the comments on “Comparison of GNSS integrated water vapor and NWM reanalysis data over Central and South America”', Laura Isabel Fernandez, 14 Jun 2019

Peer-review completion

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

ED: Reconsider after major revisions (further review by editor and referees) (15 Jun 2019) by Vassiliki Kotroni

AR by Anna Wenzel on behalf of the Authors (19 Jun 2019) Author's response

ED: Referee Nomination & Report Request started (23 Jun 2019) by Vassiliki Kotroni

RR by Anonymous Referee #1 (01 Jul 2019)

RR by Anonymous Referee #3 (22 Aug 2019)

Suggestions for revision or reasons for rejection

General Comments

The manuscript has already been revised based on the input by two anonymous referees. I find that most of their comments have been taken into account, although not all. I agree with one of the referees that the new findings reported are marginal. It is already common practise to adjust the reference heights of either the grid points in the NWM, or the height of the GNSS receiving antenna in order to sense the same height interval for the IWV. It is the location of the studied GNSS sites in Central and South America that makes this study unique (the bottom part of Figure 2) and since it in the future may be useful to other users of IWV estimates from these GNSS sites I recommend publication after that some additional issues have been taken into account.

The main issue is that I miss a discussion about the pros and cons of different methods used in order to carry out these corrections. For example, it is not explicitly stated if there are any significant differences in the method used compared to the work by Heise et al. (2009) that is referred to (see also below)?

Specific comments

p1, l3: you mention radiometers, do you mean microwave radiometers?

p2: The main point of your study is the corrections for differences in height between the GNSS antenna and the NWP grid points. In the introduction, giving the background to your work, you refer to Buehler et al. (2012) and Ning et al. (2013) but you do not mention which methods they use to carry out these corrections, and how these methods relate to the work that you are going to present?

p6, l29-35: I do not find the upper part of Figure 2 informative since there is no dependence between the ∆IWV and the mean value of the IWV. Scatter plots showing ∆IWV vs ∆z for the two NWM:s would be more interesting. This is true also for Figure 4.

p9, l5: remove "good". This is a subjective word that means different things to different readers. It is sufficient to state that Table 3 shows the results.

p9, l18: remove "good", for the same reason as above

p10, l10: You state that discrepancies are important when IWV > 20 kg/m^2. Will this statement also hold if you measure relative discrepancies (in percent)?

p10, l22: remove "successfully". It is sufficient to say that the correction reduced the differences significantly, but even better would be to give values characterising the improvement.

p10, l23-24: It will be informative to also state the percentage of stations that had ∆IWV < 1.5 kg/m^2 without applying the correction.

Technical Corrections

Overall comments:
A correct language helps the reader to understand the message(s). Unfortunately I am not a native English speaker. There are, however, a few examples below, that I just happened to notice and thinking that this is not a correct language, but I am sure there are more language improvements that should be made. Therefore, I recommend that the next version of the manuscript is proofread by a professional/native English speaker.

Units shall not be written in italic font and there shall always be a space between a value and the unit (SI rules).

vapor is the spelling in American English, although Ann. Geophys. is a European journal?

p1, l13: in islands --> on islands ?

p1, l14: over valuate --> overestimate ?

p1, l19: A complete example ... --> An example ... (this study is not complete in the sense that it does not report all comparisons ever made).

p2, l12: Radiosondes --> radiosondes

p2, l16: When written like this the ± 1.25 is interpreted as the uncertainty of the mean, but my guess is that this is the standard deviation about the mean? Please use more words to explain.

p3, l8: correspondent --> corresponding

p3, l21: Continent placed -> continent located

p3, l28: remove "respectively"?

p4, l25: locates upper than it ?

p7, l26-27: °K --> K

References: I am not sure how important this is for Ann. Geophys. but for most of the journals you do not use the common abbreviations, e.g. Journal of Geophysical Research --> J. Geophys. Res. and Geophysical Research Letters --> Geophys. Res. Lett.

p9, l24: In this examples --> In these examples

p9, l32: will result larger than --> will overestimate (and remove "that you intend to estimate")

Table 1: Why so many digits (decimals) for the geopotential?

Table 2: units are missing in the header

Table 2: also in this table there is no need for the two decimals for ∆z

Table 2: Why not include the station number also in this table, so that the reader does not have to go via Table 1 to identify the station in Figure 1?

Figure 4 caption: kgm --> kg m

--- End of Comments

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ED: Publish subject to revisions (further review by editor and referees) (30 Aug 2019) by Vassiliki Kotroni

AR by Laura Isabel Fernandez on behalf of the Authors (02 Oct 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (24 Oct 2019) by Vassiliki Kotroni

RR by Anonymous Referee #1 (06 Nov 2019)

ED: Publish subject to technical corrections (15 Nov 2019) by Vassiliki Kotroni

AR by Laura Isabel Fernandez on behalf of the Authors (18 Nov 2019) Author's response Manuscript

Short summary

Integrated water vapor (IWV) values from ERA-Interim and MERRA-2 were compared to IWV from GNSS at 67 stations in Central and South America over a 7-year period (2007–2013). The comparison considered the geopotential height differences and the mean IWV values at each station. The discrepancies between IWV from the models and IWV GNSS rose as the geopotential height difference increased. We proposed a numerical correction that compensates for this effect, which was tested with IWV ERA-Interim.