the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 10 Apr 2024
The Connection Between North Atlantic Storm Track Regimes and Eastern Mediterranean Cyclonic Activity
Abstract. A unique chain connects the flow over the North Atlantic and the development of cyclones within the Mediterranean basin. One typical mechanism includes several successive processes: upper-level flow perturbations upstream cause Rossby wave breaking (RWB) events along the jet stream, which in turn develop into potential vorticity streamers. These streamers reach the Mediterranean, and through increased baroclinicity they enhance cyclonic activity in the region. Using ERA5 reanalysis data and rain gauge measurements, we provide a systematic analysis connecting wintertime North Atlantic storm track regimes and Eastern Mediterranean cyclones and rainfall. To do so, we use different detection algorithms for each element in the chain (RWBs, streamers and cyclones). A cluster analysis of upper tropospheric eddy kinetic energy reveals a favorable configuration of the storm track where North Atlantic storms are able to propagate farther northeast. This results in upper-level potential vorticity streamers forming more eastward alongside above-average precipitation over the Levant. Meanwhile, other latitudinal positions of the storm track (southward or northward) were found to hinder cyclonic activity in the region and reduce rainfall there. The intense rainy winter of 1991–1992 is brought as a test case to exemplify this mechanism in its extreme. We show that the rain-enhancing storm track regime was prominent throughout most of this season, alongside frequent streamers in the Eastern Mediterranean.
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RC1: 'Comment on egusphere-2024-1054', Emmanouil Flaounas, 19 Apr 2024
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Review of the study entitled "The Connection Between North Atlantic Storm Track Regimes and Eastern Mediterranean Cyclonic Activity" by Sandler et al.
I have read the paper with great interest and I have appreciated the clarity of the methods. I found the results to be novel, they align with recent findings and contribute to the ongoing discussion on the role of large scale circulation in modulating Mediterranean weather and climate extremes in the Mediterranean. I certainly recommend the eventual publication with some revisions, mostly of minor nature.
If however I have a major concern, this relates to the presentation of the results. Actually, the text is rather dense and probably difficult to follow if someone is not well updated on the subject of this study. For reasons of better articulation, I would recommend smoother introductory phrases in each section of the results (or paragraphs) and a rather clear concluding remark. Some of the minor comments below point towards this direction.
- Introduction : There is a thorough presentation of the state of the art on the interactions between different large scale features and Mediterranean cyclones. Several of these interactions are described in detail, but most probably their understanding would be difficult if readers are less familiar with the Mediterranean region and the dynamics of the storm tracks. I would recommend to the authors to introduce a schematic on the main features of the mechanism that lead to Mediterranean cyclogenesis (perhaps somewhere at the end of the paragraph in line 43). One additional idea would be to be a bit more explicit on the objectives and motivations (last paragraph) and thus relocate some of the phrases/parts from the introduction to the main results in order to ease discussion of new findings with respect to previous studies. That would be of help to the reader to better place new results within the state of the art and take their time to process new findings.
- Data & Methods. This section is long and its technical nature makes it less attractive to the reader. Please consider inserting subsections. It also seems (except if I missed it) that Fig. 1c is not referenced in the text.
- Section 3.1/Fig. 3: How are densities and precipitation anomalies defined? Both colorbars seem to describe very small values.
- Section 3.2: Please reverse the two first phrases. In fact, NAO is mentioned once in the methods and thereafter it is mentioned here introducing a section with a very direct, albeit rather awkward way.
- Line 198: what is meant by "to increase the sample size"?
- Lines 200-201: Could you please provide a descriptive context about the connection of the western blocking high with the NAO positive phase? This will introduce the discussion on Fig. 5 in a smoother way and will articulate better the different parts of the paragraph.
- Line 208: The pressure low anomaly seems to persist before Lag 0 days (Figs 5b and 5d). Can you please comment on the cyclones occurrence respect to the green hatches. Is it possible that PV streamers and cyclone occurrences are not -always- sequential (in terms of time) to the max of MSLP in the black square in the black box of Fig. 5e. Actually, how would fig. 5 look if lag times are calculated respect to max of precipitation in the eastern Mediterranean?
- Relevant to the previous comment, is it possible that some of the cyclones in CL=5 dataset correspond to stationary lows in the southern side of Turkey/Cyprus? Therefore they might not really correspond to actual mesoscale cyclones?
- Probably a case study similar to Fig. 7 (or rearrangement of the last section) would be helpful here?
- Line 242: it's January 3rd 1992(?).
- Line 274: Probably it is better if you made reference to previous figures.
Citation: https://doi.org/10.5194/egusphere-2024-1054-RC1
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