the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 13 Aug 2025
Variation characteristics of sporadic-E layer in East Asia based on long-term data
Abstract. The characteristics of ionospheric intensity, spatial distribution, diurnal variation, seasonal variation and long-term variation in East Asia are studied by using the ionospheric observation data from 21 ionosonde stations in China and Japan over the past 60 years. It is found that the Es layer intensity in East Asia is much higher than the global average, and the intensity center is located near the 30° N line, and weakens to low and high latitudes. At the same time, the intensity center of Es layer is not fixed, and the intensity center migrates with diurnal and seasonal variations. It is found that the regions with stronger Es showed a long-term downward trend, while the regions with weaker Es showed a long-term upward trend in East Asia.
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RC1: 'Comment on egusphere-2025-1524', Anonymous Referee #1, 08 Oct 2025
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AC1: 'Reply on RC1', Jie Feng, 01 Nov 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1524/egusphere-2025-1524-AC1-supplement.pdf
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RC2: 'Reply on AC1', Anonymous Referee #1, 11 Nov 2025
Maybe it's my fault but I couldn't download the revised version of the paper. I didn't find a link from which to download it.
Overall, I think that the answers given by the authors are pretty fair and acceptable, except the one related to the Kriging method.
When the authors say that "Kriging interpolation is a classical spatial algorithm widely employed in studies of ionospheric and atmospheric distribution characteristics. The apparent distorted patches in the figures are primarily attributable to the rendering effects of the plotting software." I agree that "Kriging interpolation is a classical spatial algorithm widely employed in studies of ionospheric and atmospheric distribution characteristics. " but soon after when the authors say "The apparent distorted patches in the figures are primarily attributable to the rendering effects of the plotting software." cannot be accepted. What some figures in the paper are showing is not real, it is an artifact. In general, the first thing that should be evaluated is whether there exist the right conditions to apply the Kriging method, but in general, to apply any method to interpolate a discrete dataset of points. In my opinion, the information given but some figures shown by the authors is a little bit distorted.
Citation: https://doi.org/10.5194/egusphere-2025-1524-RC2 -
AC2: 'Reply on RC2', Jie Feng, 12 Nov 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1524/egusphere-2025-1524-AC2-supplement.pdf
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RC3: 'Reply on AC2', Anonymous Referee #1, 12 Nov 2025
I think the authors did their best to improve the paper. As far as I am concerned, the paper can be accepted.
Citation: https://doi.org/10.5194/egusphere-2025-1524-RC3
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RC3: 'Reply on AC2', Anonymous Referee #1, 12 Nov 2025
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AC2: 'Reply on RC2', Jie Feng, 12 Nov 2025
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RC2: 'Reply on AC1', Anonymous Referee #1, 11 Nov 2025
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AC1: 'Reply on RC1', Jie Feng, 01 Nov 2025
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RC4: 'Comment on egusphere-2025-1524', Anonymous Referee #2, 11 Dec 2025
This manuscript analyzes the morphology of sporadic E (Es) layers over the Asian region using foEs measurements from 21 ground-based ionosonde stations. While the topic is relevant and the dataset has the potential to contribute to regional Es climatology, the main conclusions presented in the manuscript are not sufficiently supported by rigorous analysis. Substantial revisions would be required before the study could be considered for publication. My detailed comments are provided below.
1. Line 112-117. The paragraph does not clearly explain how the raw foEs data were preprocessed. Key information is missing, including a) the altitude range or criteria used to select valid Es, b) how missing data were identified and removed, c) the total volume of raw data and processed data. Without these details, the reproducibility and reliability of the results cannot be evaluated.
2. Inconsistent use of median vs. mean. The manuscript should justify why the median was chosen instead of the mean or maximum value for characterizing foEs. For example, in Figure 2, the author used "median mean", but it is unclear how it was calculated. In Figure 3, the "annual mean" is used instead of the median. Why do authors need to manually select different metrics?
3. Line 244-245. The manuscript claims that foEs values during low solar activity are stronger than during high solar activity. However, Figure 8 only displays colorbar without specific values, making the conclusion unverifiable. Before drawing such conclusions, quantitative comparisons, such as the average change or spectral changes, must be made.
4. Previous studies have shown that weak foEs (< 3 MHz) are more sensitive to solar cycle modulation (see Figure 6 in Tian et al., 2024. Check https://doi.org/10.1029/2024JH000279). Table 2 in the present manuscript shows correlations between overall foEs and sunspot number, but it does not distinguish between weak and strong foEs. I encourage the authors to examine the correlations between weak/strong foEs and solar activity. Such an analysis would help clarify whether the solar cycle dependence of Es morphology is driven primarily by weak events, strong events, or both.
5. Although the manuscript maps the spatiotemporal distribution of foEs, it provides little discussion of the underlying physical mechanisms. For example, why does the nighttime Es intensity center shift northeastward? Without physical interpretation, the results remain descriptive rather than scientific, limiting the manuscript's contribution to the field.
6. Line 316. One of the main conclusions is that the Es intensity center is located near 30N. However, this conclusion appears to be based solely on the spatial distribution in Figure 2. In the other word, different interpolation methods may lead to different conclusions. To validate this conclusion, satellite observations (e.g., COSMIC-1/2) should be considered. Otherwise, the latitudinal maximum remains uncertain and may be an artifact of the interpolation procedure.
Citation: https://doi.org/10.5194/egusphere-2025-1524-RC4
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