the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 14 Nov 2022
Central European wind and precipitation compound events are not just due to winter storms
Abstract. Unlike other studies on wind-precipitation compound events, station data was employed from all seasons 1961–2020 to analyze the frequency and seasonal distribution of these events in Central Europe. The spatial pattern of the annual frequency is mainly determined by the cold half-years when the frequency generally decreases with increasing longitude (due to the decreasing effect of extratropical cyclones), but it also increases with increasing altitude (probably due to the orographic precipitation enhancement effected by strong winds). Nevertheless, wind-precipitation compound events are also generated by convective storms mainly in summer, when compound events are more equally distributed in Central Europe, with generally higher frequencies in lowlands. Five types of weather stations were distinguished according to the seasonal distribution of wind-precipitation compound events, with the percentage of summer events as the main criterion. Mostly winter type dominates in the west, mostly autumn type at the coast of the North Sea, mixed type in north-east Germany, mostly summer type in central part of Germany, and summer type in eastern part of Czechia and in south-east Austria. We also demonstrate on selected examples that compound events frequently occur at a station only in the season when both abnormal winds and abnormal precipitation events appear and are related to the same circulation conditions. This is the reason why wind-precipitation compound events are very rare at some stations, mainly in the highlands in the eastern part of the study region. We also discuss the role of the threshold for selecting wind-precipitation compound events and prove that the higher their frequency is at a station, the higher the percentage of stronger events among them. This finding highlights wind-precipitation compound events as a significant natural hazard mainly in exposed areas.
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RC1: 'Comment on nhess-2022-264', Anonymous Referee #1, 31 Jan 2023
The manuscript by Müller et al., aims to analyze Central European wind and precipitation “compound” events. Despite the topic is of interest, the manuscript fails in several key points:
- The authors are analyzing concurrent events and not real compound events. Please use the correct wording;
- More information regarding the weather data is needed (weather stations with full data, station % in altitude, missing value, etc). Data homogeneity is still a key issue when analyzing station data. Despite the authors discussed homogenization in section 4.1, there is not enough information and the methodology points for a paper from 2017 without any further information.
- I am puzzle with the use of the outdated NCEP/NCAR reanalysis. I don´t agree with the authors that the coarse resolution of 2.5°, represents well the large-scale processes. The authors should be aware that both in winter and summer, some local features (sting jets, dry intrusions, convective storms) will not be well represented in a 2.5 course resolution. The use of the state-of-the-art ERA-5 reanalysis in its native grid it´s imperative.
- Processes (drivers of the concurrent events) based analysis is missing from the entire manuscript. What summer and winter concurrent events differ? Which different drives take a role on different seasons?
The novelty of the results is also an issue. In addition, no clear objective is clearly stated in the manuscript. I don´t believe the papers as enough novelty to be included in just a journal like the Natural Hazards and Earth System Sciences.
The authors fail to put the manuscript into a larger context and discuss with the main drivers. In the present form it´s just a description of the statistical results.
Therefore, I strongly suggest the rejection of the manuscript.
Citation: https://doi.org/10.5194/nhess-2022-264-RC1 - AC1: 'Reply on RC1', Miloslav Müller, 16 Mar 2023
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RC2: 'Comment on nhess-2022-264', Anonymous Referee #2, 02 Feb 2023
Review of ‘Central European wind and precipitation compound events are not just due to winter storms’
This paper investigates co-occurring wind and precipitation events in central Europe, mainly using station data. The study makes use of the conditional probability measure and performs some linear regression between this and the longitude and altitude. The stations used are also split into groups according to the time of year at which most co-occurring events take place.
Main points
Part of the motivation of the paper is stated to be the significant difference between Western and Eastern Europe. However, there is no investigation into the causes of these differences, other than showing that they have different seasonal distributions. Since the title of the paper states that winter storms are not the only cause, it would be nice to know what the other causes are.
The introduction of the study is rather brief and does not clearly identify what the main aims or questions of the paper are. What new insight does this study hope to achieve that has not already been seen in previous work?
Some of the methods are not well described. For example, the exceedance probability does not seem to be relevant in the analysis - the use of the 98th percentile threshold is all that is needed to describe what is done. It is not clear what the goal of the linear regressions are, or exactly how this is performed. I also have reservations on the use of the NCEP/NCAR reanalysis data. Just because it has a coarse resolution, does not mean it captures the large-scale processes better than, say, a much higher resolution reanalysis. The ‘homogenization’ of the data using the reanalysis that is mentioned in the discussion is not properly described, and so it is impossible to know if the conclusions drawn are justifiable.
The results of the study are not discussed in terms of what new insight has been added compared to previous studies. Do the results with the stations give the same chi values as previous studies? In fact the discussion and conclusion sections contain only a single reference.
Minor comments
- Line 34 - a reference is needed for this statement.
- Introduction - there are other studies that have looked at co-occurring events in different seasons, just two examples are Messmer, M., I. Simmonds, 2021: Global analysis of cyclone-induced compound precipitation and wind extreme events. Weather and Climate Extremes, doi:10.1016/j.wace.2021.100324., and Catto, J. L., and A. J. Dowdy (2021) Understanding compound hazards from a weather system perspective, Weather and Climate Extremes, 32, 100313, https://doi.org/10.1016/j.wace.2021.100313.
- Line 85 - I do not think “abnormal” is an appropriate name for the high intensity events, since they are occurring multiple times per year, one could say that they are quite normal.
- Line 98 - I’m unsure what is meant by “events among abnormal winds”.
- Line 110 - In other words you are using the 98th percentile calculated only from the cold season.
- Lines 116-124 - I find this paragraph rather unclear.
- Line 137 - more detail about this linear model would be useful. How is this calculated and with which stations?
- Line 137 - I don’t find it obvious that chi increases with increasing altitude from the figure cited.
- Figure 1 - caption needs additional information of what the shading shows.
- Table 2 - why these stations? What is the justification for looking in more detail at these specific locations?
- Figure 2 - what is the scale for the size of the dots?
- Line 152 - I do not understand what “the proportion between the frequency” means.
- Line 169 - “very different from this viewpoint” - different to what?
- Line 184 - “westerly from” I think would be better as “west of”.
- Figure 8 - It took me a long time to find the legend. Please put this higher up and make it larger.
- Line 268 - More detail is required about this “statistical correction technique”. Why do you think a reanalysis at 2.5 degrees would be good for this?
- Figure 10 and the discussion of it needs more explanation. What does this mean?
- Conclusion - there needs to be a discussion of the results in the context of previous work.
Citation: https://doi.org/10.5194/nhess-2022-264-RC2 - AC2: 'Reply on RC2', Miloslav Müller, 16 Mar 2023
Status: closed
-
RC1: 'Comment on nhess-2022-264', Anonymous Referee #1, 31 Jan 2023
The manuscript by Müller et al., aims to analyze Central European wind and precipitation “compound” events. Despite the topic is of interest, the manuscript fails in several key points:
- The authors are analyzing concurrent events and not real compound events. Please use the correct wording;
- More information regarding the weather data is needed (weather stations with full data, station % in altitude, missing value, etc). Data homogeneity is still a key issue when analyzing station data. Despite the authors discussed homogenization in section 4.1, there is not enough information and the methodology points for a paper from 2017 without any further information.
- I am puzzle with the use of the outdated NCEP/NCAR reanalysis. I don´t agree with the authors that the coarse resolution of 2.5°, represents well the large-scale processes. The authors should be aware that both in winter and summer, some local features (sting jets, dry intrusions, convective storms) will not be well represented in a 2.5 course resolution. The use of the state-of-the-art ERA-5 reanalysis in its native grid it´s imperative.
- Processes (drivers of the concurrent events) based analysis is missing from the entire manuscript. What summer and winter concurrent events differ? Which different drives take a role on different seasons?
The novelty of the results is also an issue. In addition, no clear objective is clearly stated in the manuscript. I don´t believe the papers as enough novelty to be included in just a journal like the Natural Hazards and Earth System Sciences.
The authors fail to put the manuscript into a larger context and discuss with the main drivers. In the present form it´s just a description of the statistical results.
Therefore, I strongly suggest the rejection of the manuscript.
Citation: https://doi.org/10.5194/nhess-2022-264-RC1 - AC1: 'Reply on RC1', Miloslav Müller, 16 Mar 2023
-
RC2: 'Comment on nhess-2022-264', Anonymous Referee #2, 02 Feb 2023
Review of ‘Central European wind and precipitation compound events are not just due to winter storms’
This paper investigates co-occurring wind and precipitation events in central Europe, mainly using station data. The study makes use of the conditional probability measure and performs some linear regression between this and the longitude and altitude. The stations used are also split into groups according to the time of year at which most co-occurring events take place.
Main points
Part of the motivation of the paper is stated to be the significant difference between Western and Eastern Europe. However, there is no investigation into the causes of these differences, other than showing that they have different seasonal distributions. Since the title of the paper states that winter storms are not the only cause, it would be nice to know what the other causes are.
The introduction of the study is rather brief and does not clearly identify what the main aims or questions of the paper are. What new insight does this study hope to achieve that has not already been seen in previous work?
Some of the methods are not well described. For example, the exceedance probability does not seem to be relevant in the analysis - the use of the 98th percentile threshold is all that is needed to describe what is done. It is not clear what the goal of the linear regressions are, or exactly how this is performed. I also have reservations on the use of the NCEP/NCAR reanalysis data. Just because it has a coarse resolution, does not mean it captures the large-scale processes better than, say, a much higher resolution reanalysis. The ‘homogenization’ of the data using the reanalysis that is mentioned in the discussion is not properly described, and so it is impossible to know if the conclusions drawn are justifiable.
The results of the study are not discussed in terms of what new insight has been added compared to previous studies. Do the results with the stations give the same chi values as previous studies? In fact the discussion and conclusion sections contain only a single reference.
Minor comments
- Line 34 - a reference is needed for this statement.
- Introduction - there are other studies that have looked at co-occurring events in different seasons, just two examples are Messmer, M., I. Simmonds, 2021: Global analysis of cyclone-induced compound precipitation and wind extreme events. Weather and Climate Extremes, doi:10.1016/j.wace.2021.100324., and Catto, J. L., and A. J. Dowdy (2021) Understanding compound hazards from a weather system perspective, Weather and Climate Extremes, 32, 100313, https://doi.org/10.1016/j.wace.2021.100313.
- Line 85 - I do not think “abnormal” is an appropriate name for the high intensity events, since they are occurring multiple times per year, one could say that they are quite normal.
- Line 98 - I’m unsure what is meant by “events among abnormal winds”.
- Line 110 - In other words you are using the 98th percentile calculated only from the cold season.
- Lines 116-124 - I find this paragraph rather unclear.
- Line 137 - more detail about this linear model would be useful. How is this calculated and with which stations?
- Line 137 - I don’t find it obvious that chi increases with increasing altitude from the figure cited.
- Figure 1 - caption needs additional information of what the shading shows.
- Table 2 - why these stations? What is the justification for looking in more detail at these specific locations?
- Figure 2 - what is the scale for the size of the dots?
- Line 152 - I do not understand what “the proportion between the frequency” means.
- Line 169 - “very different from this viewpoint” - different to what?
- Line 184 - “westerly from” I think would be better as “west of”.
- Figure 8 - It took me a long time to find the legend. Please put this higher up and make it larger.
- Line 268 - More detail is required about this “statistical correction technique”. Why do you think a reanalysis at 2.5 degrees would be good for this?
- Figure 10 and the discussion of it needs more explanation. What does this mean?
- Conclusion - there needs to be a discussion of the results in the context of previous work.
Citation: https://doi.org/10.5194/nhess-2022-264-RC2 - AC2: 'Reply on RC2', Miloslav Müller, 16 Mar 2023
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