the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 22 Sep 2023
Testing ground based observations of wave activity in the (lower and upper) atmosphere as possible (complementary) indicators of streamer events
Abstract. For a better understanding of atmospheric dynamics, it is very important to know the general condition (dynamics and chemistry) of the atmosphere. Planetary waves (PWs) are global scale waves, which are well-known as main drivers of the large-scale weather patterns in mid-latitudes on time scales from several days up to weeks in the troposphere. When PWs break, they often cut pressure cells off the jet stream. A specific example are so-called streamer events, which occur predominantly in the lower stratosphere at mid- and high-latitudes. For streamer events we check, whether there are any changes of gravity wave (GW) or infrasound characteristics related to these events in ionospheric and surface measurements (continuous Doppler soundings, array of microbarometers) in the Czech Republic. First order signatures of streamer events were not identified in infrasound data at stations WBCI and PVCI. Supplementary ground-based measurements of GW using the WBCI array in the troposphere showed that GW propagation azimuths were more random during streamer and streamer-like events compared to those observed during calm conditions. GW propagation characteristics observed in the ionosphere by continuous Doppler soundings during streamer events did not differ from those expected for the given time period.
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RC1: 'Comment on amt-2023-167', Anonymous Referee #1, 18 Jan 2024
Kozubek et al. investigate so-called streamer events, which are occasions of outbreaks of low-latitude air masses into higher latitudes, most likely caused by planetary wave activity or wave breaking. These events can affect the circulation at higher latitudes. Therefore, the authors present an interesting approach for finding indicators of streamer events in infrasound and Doppler sounder observations. However, the authors have not found convincing signatures or encouraging results in either the infrasound or the Doppler sounding data. This is not necessarily a reason for rejection as long as the method itself is convincing; but the manuscript partly lacks detailed information about the methodology, which poses the question of whether a more detailed analysis might provide better insights towards the aims of the study. As is, it is hard for the reader to follow the approach since the interpretation of figures, tables and results is partly left to the reader. The authors do provide an outlook or recommendations of additional steps and methods for getting a more comprehensive picture; if they incorporate just one or two of these recommendations (which should not be out of the scope of this study), this might result in a more comprehensive analysis of potential indicators, also enabling more solid conclusions (even if no indicator would be found).
Therefore, I recommend a major revision of this manuscript and encourage the authors to consider the following remarks before resubmitting their manuscript.
General comments:
- The data and methods section needs to be substantially revised, especially concerning the description of the methodology.
- Choice of figure and methods, e.g. L259-263: I get the point here, but it is not very convincing to compare three values of two parameters (Table 2) with each other. And in contrast to this sentence, you actually do refer to single streamer events in the text afterwards. The only essential difference is obvious, however, in the total number of detections; this goes with the mentioned limitation that you consider much more calm periods (>150 days) than streamer events (>30 days). That said, the left-hand panels of Figs. 4 and 5 look like a portion of the respective right-hand panels. So how is this comparable at all? How about the number of detections per day? Have you considered looking at consecutive days before and after the streamer events, and how detection patterns change with the onset of a streamer event and afterwards?
- Why is it out of the scope of this study (e.g. L278) to quantify propagation effects and thus a more qualified assessment of whether there is a relation between the streamer events and infrasound detections? Modelling the propagation conditions or looking at these for, at least, one streamer event can be expected by the reader. The same holds for the source if you already indicate that modifications “shall be considered on 3rd – 7th November 2020” (indeed you refer to the WAVEWATCHIII model).
- Some phrases are a bit vague, leaving the reader alone with finding e.g. the exact numbers to get a quantifying sense for terms like “strong/small” (L51-52), “large spatial size” (L126), “high intensity (low TO3 concentration)” (L126) – please be more precise and add values to help the reader interpreting the results or understanding the criteria for manual selection. See also specific comments for additional instances.
- This study is all about streamer events. However, for someone who is not familiar with the phenomenon, the context is seemingly missing when “streamer events” are introduced the first time in L44 (there is a context with the sentence before, but this might not be clear here). At the end of the paragraph (L55), it is not fully clear how a streamer event is characterized (the typical pattern/structure described by Eyring et al. (2022) is worth to be mentioned, as it is recognizable in Fig. 1).
- The quality of the figures (except from Figs. 1&2) needs to be improved, at least based on the current PDF file (level of detail, perceptibility, size, resolution). Instead of the Table 1, could the streamer events be visualized e.g. by a time series (for instance, similar as in Fig. 6a) or as a series of well-resolved screenshots/maps (e.g. one figure per event like Fig. 1, for example showing the maximum extension of each considered streamer event)?
- It is not clear whether only three of the seven streamer events have been analysed in more detail and if considering more events (e.g. a longer time period than 16 months) could reveal more hints on potential indicators in infrasound and Doppler sounding data. Such an extended analysis using more data or examining different aspects (see comments #2 and #3) might also enable more concise discussions and conclusions. At the moment, the conclusion section mainly consists of a summary of the results (see specific comments).
Specific comments:
L37-40: These sentences would benefit from a bit more explanation.
L44-48: Here, additional references would be appropriate
L51-52: “During a streamer event the wind field changes rather strong over a comparatively small distance” – please quantify distance and strength; also: are the wind field changes strong or does the wind field change strongly?
L89: This depends on whether the streamer-related features in infrasound detections are unique or if there are other phenomena (SSWs?) that produce similar infrasound anomalies
L92/93: please rephrase
L94-96: consider rephrasing
L108: “processor” – what do you mean?
L119: “another latitudinal region” – do you mean further north/south? Or do you mean over the North Pacific Ocean?
L123: why exactly this period (16 months)? Why not, e.g., two years?
L129: “manually, by the given criterions” – table 1 does not provide any criterion, except from “streamer events” and “calm periods” – but how are these defined? This is not clear from the text so far (quantify thresholds for the criteria of L126-129). Even (or rather especially) if the manual selection is subjective, the subjective criterions (e.g. L131) need to be mentioned.
L132: “strong gradient from .. to ..” – how strong? (again, thresholds/values required)
L134: “almost no latitudinal variation” – after reading further and looking at Figures 1 and 2, this phrase needs to be clarified (no latitudinal variation within the streamer event like in Fig. 1 or within the entire hemisphere like in Fig. 2?)
L145: How is this event detected (except from the ozone-poor air mass)? Automatically or by eye inspection?
L151: As there are additional streamer events in the Northern Hemisphere, as you pointed out in the sentences L145-147, why don’t you neglect this event (L119)? (it is largest, but how large should it be, compared with another event?!)
L160: Do you consider the February event or not? It is not listed in Table 1.
L158-161: you should add that Figure 2 is an example for a calm event (as denoted in the caption only).
L253: which parameters? I suggest adding a reference
L308-311: Maybe recall here that streamer events also occur in the winter season only (September – March mentioned before)
Figure 6: The panels and their labels should be a bit larger. Consider revising the x-axis ticks.
L323-325: Why not analysing the frequency here? Given the results from WBCI (Table 2), 0.05-4 Hz does not seem to be too narrow for analysing the frequency variations
L325: How much higher? Please quantify, be more precise.
L355: What is a streamer-like event, compared to a streamer event? It was not defined before.
L387: Apart from daytime and nighttime, it is not clear (for a non-specialist, I assume) what the different frequency channels of the CDS measure (what is the difference between both channels? What are they supposed to measure?); this needs to be explained in Section 2.
L424: “larger signal amplitudes” – compared to what? (quantify)
L425 (and before in the text): “It was not rejected” sounds not like an appropriate phrase to describe results, especially not in the conclusions. Better would be something like “Signal amplitudes are the same …” or “there is no difference between …” here.
L428: “a transient decrease of the frequency …” – How do you interpret this finding? What does this mean, e.g. in terms of the propagation conditions? What do you conclude from this finding?
L429: “Based on these results, infrasound measurement at a single infrasound station cannot be recommended as a reliable sole indicator of streamers.” – From which results do you conclude this – and why? This needs to be discussed somewhere. The sentence comes a bit surprising after you describe the transient frequency decrease in the sentence before.
L443-450: this is a summary of the results section, but what is the conclusion?
Technical corrections/suggestions:
L13: rephrase (at least the parenthesis) - dynamics in both parts of the sentence sounds strange, like “for understanding of atmospheric dynamics, it is important to know the dynamics and chemistry…”
L35: dynamic processes -> dynamical processes
L42: comma after “When planetary waves break”
L45: originate by -> originate from
L46: the -> their (assuming that you mean the characteristics of planetary waves and streamer events), They -> Streamer events
L59: tens km -> tens of kilometres (or 10 km?)
L94: follow -> follows
L110: brackets for years of the references
L126: “distinguished” – how is this meant? selected?
L130: weather -> whether, effect -> affect
L169: the reference is misplaced
L173: Full stop missing after “tetragon”
L181: 10 or 20 Hz sampling rate?
L182: 1-min mean values [add: of the absolute pressure data]
L210-212: Merge three sentences into one: “All analyses will be done with respect to the streamer events and calm periods shown in Table 1.”
L216: January 2020 – April 2021
L232: compared to
L238: The reference does not fit to the text, maybe you mean this publication instead: https://doi.org/10.1093/gji/ggy520
L239: high particularly -> particularly high
L243: occurred on -> occurred from
L251: full stop missing
L263: are [the] same
L266: … presented in Table 2 and depicted in Figure 4.
L271: not sure if webpages are accepted as references, but at least it should be noted when these were “last accessed”
L299: suggest changing “included in the study the performance of which is optimal” -> “included in the study because its performance is optimal”
L304: suggest changing “occurred in the season of winter stratospheric westerlies” -> “occurred in the winter season when stratospheric westerlies persist”
Figure 6: I recommend using a colormap other than ‘jet’/’rainbow’ (see, e.g., https://doi.org/10.1038/s41467-020-19160-7)
L325: “departures” -> “onsets” ?
L328: the same
Section 3.2: different date format used in the text
L347: 0.0.5 should be corrected
L381: criterions (or more common: criteria)
L389: corresponds -> correspond
L392: “who showed” -> which showed” (the investigation)
L433: observer -> receiver
L440: “it will be to benefit of future studies” – do you mean “it will be a benefit to future studies” ?
Citation: https://doi.org/10.5194/amt-2023-167-RC1 - AC1: 'Reply on RC1', Michal Kozubek, 01 Apr 2024
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RC2: 'Comment on amt-2023-167', Anonymous Referee #2, 22 Feb 2024
- AC2: 'Reply on RC2', Michal Kozubek, 01 Apr 2024
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AC3: 'Comment on amt-2023-167', Michal Kozubek, 07 Apr 2024
We have improve and redone major part of our paper and all changes or answers have been submited.
Citation: https://doi.org/10.5194/amt-2023-167-AC3
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