A Refined Regional Model for Estimating Pressure, Temperature, and Water Vapor Pressure for Geodetic Applications in China

Round 1

Reviewer 1 Report

Although the idea of the study is not absolutely new, it has an interesting approach and considerable results

Author Response

Thanks！

Reviewer 2 Report

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Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

A refined regional model for estimating pressure, temperature, and vapor pressure based on ERA5 reanalysis data

Li et al. 

Summary

The authors aim is to provide a methodology for obtaining accurate hourly T, P, and e on the ERA5 0.25x0.25 grid.  The overall objective of the study could be useful for calculation of GNSS derived total column water vapor but the methods of the authors and their improvement over simply using ERA5 2-m meteorological parameters is unclear to this reviewer.  Please see the more detailed comments below.  I was unable to sufficiently review the manuscript without first understanding what is being validated.  It seems that the authors have corrected profiles of T, P, and e to the actual surface of the earth using ERA5 and height correction techniques.  They then validate these calculated T, P, and e values with an independent sample of ERA5 data from a separate year.  But it is not clear how they get the ERA5 data to the actual surface to compare with their model without using their model.  I recommend the authors provide a more clear discussion of what aspects of their model in particular are an improvement over the ERA5 2-m T and q and derived P and e quantities at this level before publication.

Detailed comments:

p. 1, line 31: ERA5 is a reanalysis and is not available in real-time.

p. 2, line 67: What do you mean by a Tm and vapor pressure “decrease factor”.  This needs further discussion.

p. 5, lines 150-151: This statement is not correct.  The semi-diurnal pressure variations are well-known and are due to atmospheric tides.  See, for example, Aplin, K. L., and P. D. Williams, 2011: Meteorological phenomena in Western classical orchestral music. Weather, 66, 300–306, doi:10.1002/wea.765.  The semi-diurnal variability in air temperature is due to the tides in pressure.

p. 6, section 3.3: It is not clear why the authors are corrected 2-m temperature and vapor pressure to the surface values.  Generally speaking, 2-m is the standard height to examine “surface” temperature and moisture values in meteorology and are used in, for instance, bulk formulae of surface heat and moisture fluxes.  If converting GPS to PWV one would have to correct to the height of the GPS antenna, which would vary from station to station and is generally not at the surface.  Surface meteorological observing stations also use 2-m for their thermodynamic sensors and 10-m for their wind sensors.

p. 7, line 229: While the authors are using a different year (2017) to validate their CPTw model than the years of ERA5 data used to calibrate their model (2012-2016), this is not really validation since ERA5 was used to determine the coefficients for the seasonal and diurnal cycles in the CPTw model.  It seems like it would be more valuable to validate the coefficients in the model with China’s vast surface meteorological network.

P. 7, lines 224-225 & lines 229-232: What height are the authors correcting the ERA5 temperature, pressure and vapor pressure to?  Why not just use the 2-m temperatures provided by ERA5?  What level from ERA5 are you comparing to your CPTw model?  Literally at the surface?  Are you correcting the 2-m ERA5 to the surface too?  This is very confusing.

Minor corrections:

p. 1, line 15: Define GPT and GPT2w.  You do this in the Introduction but I think it needs to come when the acronyms are first used.

p. 1, line 23: Define CPTw.

p. 2, line 77: Define ERA5 here rather than in the next section.

p. 4, line 138: Change EAR5 to ERA5 - typo.

p. 6, line 195: Change “what” to “these”, referring to the FFT power spectrums described in the previous sentence.

Author Response

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Reviewer 4 Report

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Comments for author File: Comments.pdf

Author Response

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Round 2

Reviewer 2 Report

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Comments for author File: Comments.pdf

Author Response

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Reviewer 3 Report

I thank the authors for their replies to my confusion over the methods in the paper.  I am happy with the edits made to clarify the presentation and recommend publication with minor grammatical issues addressed.

Author Response

Thanks. We have carefully checked and edited the manuscript, and the edited words/sentences have been highlighted in red in the revised manuscript.