the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 01 Nov 2023
Comment on “Transport of substantial stratospheric ozone to the surface by a dying typhoon and shallow convection” by Chen et al. (2022)
Xiangdong Zheng
Wen Yang
Yuting Sun
Chunmei Geng
Yingying Liu
Abstract. Chen et al. (2022) analyzed the event of rapid nocturnal O3 enhancement (NOE) observed on 31 July 2021 at surface level in the North China Plain and proposed transport of substantial stratosphere ozone to the surface by Typhoon In-fa followed by downdraft of shallow convection as the mechanism of the NOE event. The analysis seems to be valid in the view-point of atmospheric physics. This comment revisits the NOE phenomenon on the basis of the China National Environmental Monitoring Center (CNEMC) network data ever used in Chen et al. (2022), together with the CNEMC data from Zibo (ZB), and O3, NOx, PAN and VOCs data from the Zibo supersite operated by China Research Academy of Environmental Sciences (CRAES). We found (a) Ox (O3+NO2) levels during the NOE period approaching to those of O3 during 14:00–17:00 LT; (b) the relationship between O3 and PAN (peroxyacetic nitric anhydride) consistent with dominance of chemical and physical processes within the boundary layer, and (c) estimated photochemical ages of air mass being shorter than one day and showing no drastic increases during the NOE. We argue that the NOE was not caused by typhoon-induced stratospheric intrusion but originated from fresh photochemical production in the lower troposphere.
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Xiangdong Zheng et al.
Status: open (until 13 Dec 2023)
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RC1: 'Comment on egusphere-2023-2336', Anonymous Referee #1, 22 Nov 2023
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The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2336/egusphere-2023-2336-RC1-supplement.pdf
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RC2: 'Comment on egusphere-2023-2336', Anonymous Referee #2, 30 Nov 2023
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The study from Zheng et al. is a comment on the study by Chen et al. (2022). Chen et al. (2022) demonstrated that the intrusion of stratosphere ozone induced by Typhoon Infa served as a potential source of surface ozone, and the following shallow local mesoscale convective systems facilitated the downward transport of this potential ozone source to the surface, and led to a nocturnal ozone enhancement (NOE) event in the North China Plain (NCP). Zheng et al. analyzed observations (including PAN, VOCs) from the ZiBo supersite at eastern NCP, and argued that the NOE event originated from fresh ozone photochemical production in the lower troposphere rather than from the stratosphere as pointed out by Chen et al. (2022). This is supported by 1) comparable nighttime surface Ox and daytime O3 levels, 2) a strong correlation between PAN and ozone during the NOE event, and 3) the short photochemical ages of air mass. Overall, the study provides strong observational evidence on the conclusion, and is well-designed and well-written. I suggest some revisions before publication.
While I agree with Zheng et al. that the mixing of ozone produced photochemically and stored in the residual layer has a large contribution to the Zibo NOE event, it does not necessarily exclude the possibility of stratospheric contribution proposed by Chen et al. (2022). Zheng et al. mainly used observations at ZiBo city, however, as seen from Figure 8 of Chen et al. (2022), there is limited vertical atmospheric activity near the ZiBo supersite, as the main convective zone is located in the western Shandong Province. So the difference in the study region between Chen et al. (2022) and Zheng et al. may also contribute to the different conclusions. I would suggest the authors consider this point in their analysis.
One small comment is to clarify O3 as “daytime O3” and Ox as “nighttime Ox” in Table 1.
Citation: https://doi.org/10.5194/egusphere-2023-2336-RC2
Xiangdong Zheng et al.
Xiangdong Zheng et al.
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