the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 20 May 2026
Comparing AERONET integrated water vapor with GNSS over the Arctic in the context of former comparisons with radiosondes and reanalyses
Abstract. The Integrated Water Vapor (IWV) determination in the Arctic is very important for atmospheric-climate studies. Different measurements and techniques are used for this purpose, having in general low spatial and temporal resolutions, except the Global Navigation Satellite Systems (GNSS), especially in the Arctic due to extreme weather conditions. In this work, the comparison of IWV measured by sun photometers (SP) from AERONET (IWVSP) and IWV measured by GNSS (IWVGNSS) at Arctic sites, is carried out. Taking coincident hourly averaged data IWVSP from 13 AERONET and 35 IWVGNSS sites were selected, covering the period 1997 to 2023. The comparison IWVGNSS versus IWVSP presents very good statistic indicators with the range of absolute and relative Mean Bias Error MBE (rMBE) of 0.007(0.8%)–0.091(15.4%) cm and standard deviation STD (rSTD) of 0.047(6.5%)–0.123(14.4%) cm. The positive bias at all sites detects a dry bias of SP respect to GNSS. Linear regression slopes are greater than 1 at nine sites, and lower at four. Those slopes lower than 1 appears related to higher frequency of IWV lower values (very dry conditions). All sites present Pearson correlation coefficients higher than 0.96, showing a low data dispersion. Results show that for IWV low values, less than 1.5 cm, SP predominates over GNSS, and the opposite when IWV values increase. This work complements two previous ones, where IWV from radiosondes and reanalysis were compared with IWVSP. Although the different data-bases, for coincident hourly, the highest values of IWV are given by GNSS, radiosonde, SP and reanalysis in this order.
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Status: open (until 20 Aug 2026)
- RC1: 'Comment on egusphere-2026-2374', Anonymous Referee #1, 15 Jul 2026 reply
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- 1
General comments
The manuscript addresses an interesting and relevant topic. Comparisons of this type are still relatively scarce in the Arctic, and the use of an original photometer dataset represents a valuable contribution. However, I have several major concerns that should be addressed before the manuscript can be considered for publication.
First, the English language requires substantial revision, and the overall organization of the manuscript should be improved. Several sections are difficult to follow, and the presentation of the methodology and results is not always sufficiently clear. Second, a number of statements and conclusions are not adequately supported by the existing literature.
In addition, important methodological details regarding the datasets are missing. In particular, the manuscript should provide:
Maybe these methodological aspects should preferably be included in the Data or Instrumentation section of the manuscript.
I therefore recommend acceptance after major revision.
Specific comments
Line 22: For consistency with the rest of the manuscript, please use subscripts for IWVGNSS and IWVSP.
Line 27: Please reformulate the sentence "the positive bias at all sites detects a dry bias".
Line 29: The expression "a low data dispersion" is unclear. It may be more appropriate to refer to the consistency or agreement between the time series.
Lines 46-57: Please revise the wording and improve the flow of ideas in this paragraph, particularly the transitions between sentences.
Line 47: The expression "More recently" is not appropriate for a technique introduced in 1992 (Bevis et al., 1992).
Section "Instruments": Consider renaming this section to "Instruments and Data". Why not also introduce the radiosonde and reanalysis datasets in this section?
Subsection "Sun Photometer": Please provide more information about the dataset. What is the temporal resolution? What are the operating conditions and measurement schedule? What are the main uncertainties associated with the technique?
Lines 81-82: Please briefly summarize the main findings of the cited studies.
Subsection "GNSS": Please note that these data may be affected by limitations related to the relatively low spatial and temporal resolution of the VMF1 grids used by NGL. The authors may wish to discuss this issue and refer to: https://doi.org/10.5194/essd-15-723-2023.
Lines 110-111: Why is the uncertainty associated with IWV_SP discussed here rather than in the previous subsection?
Lines 113-114: It would be useful to briefly recall the method used for the vertical extrapolation of IWV.
Table 1: Why not include the radiosonde information in this table as well?
Lines 132-140: Please reformulate this paragraph for improved clarity.
Line 156: Please provide statistics describing the agreement among the GNSS datasets used to generate the average product (e.g., mean differences, standard deviation, minimum and maximum values).
Figure 2: I suggest moving this figure later in the manuscript, closer to the discussion in Section 4.2 where it is first described and interpreted.
Subsection 3.3: This section does not seem to warrant a dedicated subsection and could be moved to an appendix.
Lines 197-200: This sentence is difficult to understand and should be reformulated.
Table 3: Please include the number of comparison points used in each analysis to allow readers to assess the statistical significance of the results. In addition, it may be useful to separate the reanalysis comparisons by region in order to provide more insight into the spatial variability of the results.
Section 4.3: Consider merging Sections 4.3 and 4.4 into a single Discussion section.
Lines 239-240: Please reformulate this sentence.
Line 270: Please add an appropriate reference.
Lines 288-292: This paragraph is not clear and should be rewritten.
Line 293: I suggest replacing "demonstrated" with "confirmed".
Subsection 4.5: I recommend moving this subsection before the current Sections 4.3 and 4.4, especially if those sections are merged into a Discussion section.
Line 312: Please add an appropriate reference.