The intrinsic relationship between cyclones, anticyclones, and Rossby Wave Breakings in the North-Atlantic
Abstract. Rossby wave breaking events describe the last stage in the life-cycle of baroclinic atmospheric disturbances. These breaking events can strongly influence the large-scale circulation, and are also related to weather extremes such as heat waves, blockings, and extreme precipitation events. Nonetheless, a complete understanding of the synoptic-scale dynamics involved with wave breaking events is still absent. Here we highlight the fundamental relation between low-level weather systems and upper-level wave breaking events in the North Atlantic region, by combining a storm-tracking technique together with a wave breaking detection algorithm. We show that Anticyclonic Wave Breaking (AWB) events are associated with a strong upper-level ridge and a low-level anticyclone to its east, which are both located in the anticyclonic side of the jet. During the breaking, a strong cyclone is often found to the north-northwest of the anticyclone, while a weaker one is often found to its south-southeast. Time evolution composites centered around anticyclones during AWB show that as the downstream trough wraps anticyclonically to the east and south of the ridge, the upper-level jet weakens to the south, hence the upper-level jet becomes more split into an upstream poleward tilted jet, and a downstream zonal jet. In addition, the Sea Level Pressure (SLP) anomalies rotate in an anticyclonic manner relative to each other, such that the initially zonally oriented low-high SLP anomaly dipole become meridionally oriented by the end of the life-cycle (low-above-high). On the contrary, Cyclonic Wave Breaking (CWB) events are associated with a strong upper-level trough and a low-level cyclone to its east, which are both located in the cyclonic side of the jet. An additional anticyclone is often found to the northeast of the cyclone. Time evolution composites centered around cyclones during CWB show that as the downstream ridge wraps cyclonically to the east and north of the trough, the zonal and more southward shifted upper-level jet weakens further to the north. A relative cyclonic rotation is observed at low-levels, such that a high-above-low SLP anomaly dipole is found by the end of the life-cycle. A simple kinematic interpretation is suggested for the poleward and equatorward shifted jets associated with AWB and CWB events, respectively. Anomalous life-cycles of anticyclones during CWB events and cyclones during AWB events are also discussed.
Talia Tamarin-Brodsky and Nili Harnik
Status: final response (author comments only)
- RC1: 'Comment on egusphere-2023-534', Anonymous Referee #1, 18 Apr 2023
- RC2: 'Comment on egusphere-2023-534', Anonymous Referee #2, 26 Apr 2023
- RC3: 'Comment on egusphere-2023-534', Anonymous Referee #3, 26 Apr 2023
- AC1: 'Comment on egusphere-2023-534', Talia Tamarin, 01 Jun 2023
Talia Tamarin-Brodsky and Nili Harnik
Talia Tamarin-Brodsky and Nili Harnik
Viewed (geographical distribution)
Review of the manuscript entitled “The intrinsic relationship between cyclones, anticyclones, and Rossby Wave Breakings in the North-Atlantic” by Tamarin-Brodsky and Harnik
It is a well-written and interesting paper that contributes to the knowledge on Rossby wave breaking and their link with cyclones and anticyclones. The methodology is appropriate. I only have relatively minor remarks and technicalities that need to be addressed before publication. They are listed below following the order of the manuscript.
Main body of the manuscript:
Line 67: In order to relate to the expressions given later in the same paragraph, maybe add (u’v’) after “eddy momentum fluxes”.
Line 71: Please state that q is here the relative vorticity (and not the potential or absolute vorticity).
Lines 142-143: Cyclones correspond to positive values of relative vorticity and anticyclones to negative values. Therefore, maxima in relative vorticity correspond to cyclones and minima to anticyclones. However, the threshold given here (10-5 s-1) is positive. Is it an absolute value of relative vorticity? The same comment applies for Fig. 3. The intensity represented with the colors and threshold given in the caption are always positive even for the anticyclones (panels b and d). Also, write somewhere that the intensity of the cyclones and anticyclones is given by the relative vorticity at 850 hPa at the cyclone centre location (and not an average or maximum value in an area around the cyclone).
Line 155: Can the authors justify the use of the 350 K isentrope for detecting the RWB? Previous studies have used several isentropes to make sure that they cover the tropopause at all mid-latitudes (see for example Fig. 2a in Martius et al. (2007) (https://doi.org/10.1175/JAS3977.1) for the location of the tropopause relative to the isentropes). One can expect more (less) frequent AWB (CWB) at 350 K than at a lower isentrope. As the actual frequencies of AWB and CWB are not given in Fig. 1, it is difficult to get an idea of the relative frequency of the two wave breaking types.
Line 166: How do the authors define “maximum overturning”? Please precise.
Lines 166-168: How do the authors choose these three threshold values? Are they taken from a previous study?
Lines 180, 227: I believe that “recovers” is not the right word in this context. I suggest to change this word's occurrences with “in agreement with” or “in accordance with” previous studies or a particular study. In lines 180-181, I suggest to cite Strong and Magnusdottir (2008) for example and maybe other studies.
Line 252: ”anticyclone locations are mostly below the upper-level ridge”. The meaning is not clear. I suggest to replace “below” with within.
Lines 263-268: Only the cyclones positions are discussed. The anticyclones positions need to be discussed in this paragraph as well.
Line 268: “maximum” -> most frequent.
Line 283: Are the displacement values significantly different? Could the authors provide a standard deviation?
Lines 284-285: I do not find the statement about the anticyclones being located at higher latitudes convincing. First, because a reference position is needed: higher than what, than anticyclones positions during AWB or cyclones positions during CWB? Second, because apart form the local maximum over Greenland, the rest seems to be at lower latitudes than the cyclones during CWB and anticyclones during AWB. Moreover, the reference of Fig. 4 is missing to understand the full sentence.
Lines 303-305: This sentence is not very understandable to me and needs to be adjusted. Does the “in the next section” refer to section 5? It is not clear.
Line 335: “The negative upper-level meridional velocity … is mainly due to the intensifying anomalous ridge-trough system”. How can the authors know that the southward meridional wind is due to the amplifying ridge-trough and not the cause for the amplification of the ridge and trough?
Line 340: It is not clear to me where the “background anticyclonic shear” is visible. Could the author precise it? Isn’t there also cyclonic shear on the southern side of the anticyclone?
Line 418: “an upper-level breaking in the corresponding sense is often found at upper-levels (Fig. S4 and Fig. S5)”. To me, it is not clear from these two figures that there are any wave breaking happening. Therefore, I suggest to add the wave breaking frequency (as a percentage of the number of events considered in the composite and not normalised, see my previous comment above).
Section 5: Could the authors also display T = 1 and T = 2 days on Fig. 9? It would help to see even more clearly how different these “anomalous life-cycles” are from the regular life cycles displayed in Figs. S4 and S5, which display T = -2 to T = 2 days.
Lines 482 and 485: “while anticyclones are found to the NE of the cyclones” and “generally to the NE of the cyclones” seem to have the same meaning and the second occurrence to be an unnecessary repetition of the first. I suggest to remove the second occurrence.
Typos and others:
Title: North-Atlantic -> North Atlantic
Line 37: (CWB),(e.g. Fig.1b) -> (CWB) (e.g. Fig. 1b)
Line 60: Section 22.2 -> Section 2.2
Line 129: Conclusion -> Conclusions
Line 135: December-January -> December-January-February
Lines 132-133: velocities -> wind
Line 142: 850 hPa vorticity -> 850 hPa relative vorticity
Line 143: centeres -> centers (US spelling) (or centres UK). “centers” is used on line 147.
Line 143: 1.10-5 -> 10-5. The 1 does not seem useful.
Line 176: centeroid -> centroid
Line 178: braking -> breaking
Line 198: Full stop missing at the end of the sentence.
Line 199: storm-ceneterd -> storm-centered
Lines 216, 223: show -> shows
Line 223: a low-PV… a high-PV -> a low-PV tongue … a high-PV tongue
Line 225: deccelerate -> decelerate
Line 226: composite -> composites
Lines 260, 262, 263, 264, 267: “??” The references to Fig. 4 did not appear well.
Lines 261-262: magnitudes -> intensities
Line 9 and throughout the manuscript: I do not think it is correct to “centre around”. I would rather say “centre on” the (anti)cyclone location.
Line 303: subsection -> subsections
Lines 343-344: Tamarin and Kaspi, 2016 -> Tamarin and Kaspi (2016)
Line 368: anticycloniclly -> anticyclonically
Line 402: Fixing -> Adjusting
Line 406: jet is remains -> jet remains
Line 411: it east -> its east
Line 415: In section (4a) and (4b) -> In sections 4.1 and 4.2
Line 460: Fig. ??a. The reference to the figure (Fig. 4?) did not work.
Line 520: seem -> seems
References: Almost all capital letters are missing in the titles of the referenced articles, the journal names should be abbreviated and the doi provided (see https://www.weather-climate-dynamics.net/submission.html#references). For example, in the first reference of Benedict et al., north atlantic should be North Atlantic, Journal of the Atmospheric Sciences should be abbreviated, and the doi provided. The issue number is not necessary (for example in Eady 1949).
Figure 4: In the sentence before the last: denote -> denotes
Figure S8: “after to” -> after
Overall, I suggest to replace “velocity” with air velocity, wind, or wind speed.
Several figures display PV at 250 hPa whereas, RWB events are detected in PV fields on the 350-K isentrope (line 155). Although the authors wrote that the results are similar when detecting RWB in PV at 250 hPa and use the wind at 250 hPa, I still find it inconsistent to display PV at 250 hPa and not at 350 K since it is the field used to detect RWB.
About the cyclone-centred figures: it looks like a “random” PV isoline is plotted. I assume that the contour value has to be changed to illustrate the authors’ point, but the reason for using different contours on different figures could be stated. Also, as an example why choosing the 3.2 PVU contour in Fig. 6? Was the 3 PVU contour not good enough?
Figure 1: I understand why the authors are representing the wave breaking frequencies with normalised pdfs, but information about the relative (and actual) frequency of the two types is lost, isn’t it? Or do AWB and CWB have the same frequency? The year of the two particular events (panels a and b) is not given in the caption. Please add it and maybe save space by shortening the dates such as, e.g., 7 Dec YEAR 00UTC. Finally, I suggest to increase the size of the domain to the east, such as to be more consistent with the domain mentioned in line 171, that extends to 20ºE (starting the figure at 260ºE is fine). It would also be great if the longitude values in the x-axis could correspond to the values in the text (expressed with ºW), that is instead of “270, 300, 330, 360”, -90, -60 -30 and 0 could be used.
Figure 2c: How do the authors explain that the low-PV streamer is not as distinct as for the AWB composite? A blue tongue is not present.
Figure 3: See my comment above about the intensity of anticyclones. Anticyclones should have negative relative vorticity but the colorbar shows positive values for both cyclones and anticyclones. Could the author mention that the absolute relative vorticity is used (if that is indeed the case)? Also, why is the PV contour not the same as in Fig. 2? Aren’t they composites over the same wave breaking events?
Figure 5: It would be great to have x-axis labels. Moreover, the name of the second row needs to be changed: Antiyclones -> Anticyclones
Figure 7: The letters designating the panels a, b, and d are not well aligned. I would remove the Ucross as x-axis label and replace them with the columns title. I would change “U250 tav” to U250 with a bar over U to be consistent with the notation in the text (line 329). If the authors make this change, they can also change “U250 total” to U250. The red and pink lines are not very well distinguishable. A lighter pink would be maybe better.
Figure 8: “Same as Fig. 4”. Isn’t this figure the same as Fig. 6?
Figure 9: On the top label of the middle figure it should be T=-1 and not T=1.
Units in captions and text:
- the authors often use ms-1 as unit for wind. I personally find this writing misleading as it can refer to millisecond and not meters per second. Therefore, I suggest to add a white space in between the m and the s: m s-1.
- the authors use both mb and hPa as unit for pressure. Choose one and keep it all along the manuscript.
Figure S2: It is similar to Fig. 4 of the manuscript and not to Fig. 3.
Figure S3: The same colormap as Fig. 1c,d could be used for an easier comparison.
Figures S4, S5 a,f: Do these figures actually show T=-2 days and not T=-3 days? In the manuscript T=-3 days is used. Moreover, please state that the PV anomalies are the contours (top row), the zonal wind at 250 hPa the shading and the SLP anomaly the contours (bottom row).
Figure S5: This figure is the same as Fig. S4 and not S1.
Figures S6 and S7: The title of panel a shows T=-3, but the caption says T=-2 days. Please correct.
Figure S7: This figure is the same as Fig. S6 and not S3.