11 Mar 2026
| 11 Mar 2026
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).
A polar mesospheric precursor of sudden stratospheric warmings observed by the Aura Microwave Limb Sounder
Abstract. The observations of the Aura Microwave Limb Sounder (Aura/MLS) indicate the existence of a polar mesospheric precursor of major sudden stratospheric warmings (SSWs). The geopotential height data of Aura/MLS from 2004 to 2021 show that a burst of a 4 day-oscillation (zonally symmetric wave with zonal wavenumber zero) occurs at the stratopause and in the mesosphere at 80° N about 17 days before the central date of the SSW. The detection of this precursor in forecast analyses of weather and climate models has the potential to extend the subseasonal forecast of SSWs from three to five weeks.
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Using an analysis of Aura MLS data from 2004 to 2021, the paper identifies a mesospheric precursor for Sudden Stratospheric Warming events in the northern hemisphere. The study presents a valuable result which has potential for improving extended medium-range weather forecasts. The results are presented logically and the overall readability is good. However, I feel much more careful analysis is required to make the manuscript suitable for publication in Atmospheric Chemistry and Physics. Therefore, I recommend the manuscript to undergo major revision before it can be considered for publication.
In my opinion, the introduction section has scope for improvement. It would be appropriate to include a somewhat detailed discussion on the zonally symmetric oscillations especially during SSW events. It is also important since this aspect has not received much attention in contrast to stationary or traveling planetary wave enhancements during disturbed winter conditions.
Overall, the amount of new results presented in the manuscript is rather small. Several of the figures can be combined and further detailed analysis can be included. In my opinion, Figures 1-2, Figures 4-5 and Figures 6-7 could be combined.
Why are only major SSW events included in the analysis? Are minor SSW events accompanied by such precursors? If not, why are they absent? If so, what factors determine the occurrence of the precursor exclusive to major SSW events?
Another related question would be, are there S0 enhancements other than during SSW events? Has this been examined?
While the manuscript presents an interesting mesospheric precursor for SSW events, the interpretation is rather shallow and lacks detailed dynamical reasoning. By now, it is well established that zonally symmetric oscillations are primarily generated by non-linear wave-wave interactions. In the present study, there is no attempt made to identify the causative mechanism responsible for the early occurrence of 4-day oscillation in the mesosphere. I think it would be worthwhile to look at what wave modes contribute to the generation of the identified 4-day oscillation and, in particular, the relationship of the S0 precursor, if any, to SPW1 and SPW2 which are generally found to enhance during SSW events.
I would also urge the author to include a discussion on how the results presented in the manuscript are different from the ones presented already in previous literature, say, for instance in Pancheva et al (2007) and Zhao et al (2025).
Given the large variability that has been historically observed among SSW events, what makes the occurrence of the 4-day S0 approximately 20 days prior to major SSW events particularly robust?
I believe it would also be appropriate to have more details on the analysis techniques, such as for the bandpass filtering and the estimation of S0 amplitudes, in the manuscript text itself for improving the overall readability.
L 140: It is stated that the burst at longer periods is not well defined compared to the one at shorter periods. This has to be substantiated by estimating the confidence levels. It appears from Figure 8 that the oscillation at 10-12 days period is stronger than the one at 4-days period.
Technical comments:
L 107: change ‘controlled’ to something like ‘examined’.
Page 5, Paragraph 1: The figure number is incorrectly written. It should be Figure 5.
L 130: Insert ‘at’ after times.