Estimating Uncertainties of Simulated MW Sounding Sensor Brightness Temperatures

Round 1

Reviewer 1 Report

Lack of novelty and please clarify innovation. The presented method has been known and I am missing some motivation for the study.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Major comments

 

1) The title of this paper is potentially misleading. This paper presents a discussion of the comparisons of MW sounders with forward-modelled NWP model fields and GNSS RO profiles. The manuscript does not seem to provide a comprehensive assessment of all the uncertainties in these comparisons. 

 

2) There is a quite disturbing use of antenna temperature and sensor-derived brightness temperature. Those are not synonyms, since in order to derive the sensor-derived Tbs one needs still to apply various steps, e.g. antenna pattern correction.This should be better clarified in the text.

 

3) There is no assessment/discussion of representativeness errors introduced by NWP models, nor a discussion of the actual scales represented by the RO soundings. RO soundings by design have quite coarse horizontal resolution, quite different from those of the MW sounders. The representativeness of these scales, from the troposphere boundary layer, to the mesosphere, is not particularly discussed.

 

3a) The uncertainties due to the instruments' sampling being different from the model or GNSS RO may dominate the uncertainty budget of the comparison, yet are not particularly discussed in the paper.

 

3b) The use of GNSS RO in the lower troposphere is highly complex, due to the presence of WV and the actual structure of the planetary boundary layer. Perhaps comparisons with the microwave channels that peak above the mid troposphere should be considered.

 

4) The radiative transfer model themselves are affected by their own uncertainties, (e.g. spectroscopy, approximations), etc. and this is only collaterally discussed, e.g. by assuming (without explaining) that the profiles considered are clear sky profiles only. It would be interesting to see the actual PDFs of the various differences, in order to assess the statistical behavior of the various contributing terms.

 

4) The definition of uncertainty in Equation (6) is not consistent with conventional definitions, and not fully explained. There are underlying assumptions on the distributions of the terms considered that are not clearly explained.

 

4a) The term "uncertainty" is often used where "bias" or "difference" is meant.

 

5) The Normalized Scaling Factor (NSF) is introduced without any clear explanation/justification. It is not very clear what it bring, apart some sort of scale analysis of the various contributors.

 

6) what is the error introduced by time interpolation? is there any way to consider that?

 

7) It is very hard to tell from figure 5 all the details mentioned in the text. maybe these plots are not so relevant.

 

8) 575: RMS and STD are not the same. This confusion appears throughout the paper.

 

9) section 4.3 is very long, it could be helpful to split this section in sub sections to help the reader to follow the various discussions.

 

10) 738-739: this is an interesting result, warranting a discussion on antenna pattern correction, eventually.

 

Minor comments

 

 

The quality of the figures needs to be improved in the documenting order to improve readability. Some compression artifacts are present on some figures (e.g. figure 4).

 

400-406 A table with the ROIs would help.

 

Figure 1: better use “intervals” or “validity time” instead of “periods” (ECMWF HRES Box).

 

300-302 The selection criteria should be discussed, in order to explain why these particular criteria were selected.

 

530-531 GNSS RO is mentioned in the text, but it does not appear in figure 8 nor in the caption to the same figure.

 

Figure 12: It is not east to go back and forth in the text to reinterpret the caption.. 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The work entitled “Estimating Uncertainties of Simulated MW Sounding Sensor Brightness Temperatures” investigates and characterises the uncertainty of radiative transfer model simulated MW Tbs, by implementing a new method based on a statistical analysis and comparison of two community RTM datasets .
The topic is of relevance, as these uncertainties are crucial for correctly monitoring the space-born observed MW sensor antenna temperature.
This is a good work, full of details, the scientific community will benefit from its analysis and findings.
I do not have major concerns regarding the article nor its content, and I would recommend publication after minor revision, to further ensure there are no typos or mistakes

The English is fine, I would just recommend a further check to be sure.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

I would like to thank the Authors for the work done, providing the various clarifications and improving the overall paper. I consider now this paper fit for publication.