the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Impact of aerosol optics on vertical distribution of ozone
Shuqi Yan
Bin Zhu
Shuangshuang Shi
Wen Lu
Jinhui Gao
Hanqing Kang
Duanyang Liu
Abstract. Tropospheric ozone, an important secondary pollutant, is greatly impacted by aerosols within boundary layer (BL). Previous studies have mainly attributed ozone variation to either aerosol-BL or aerosol-photolysis interactions at near surface. In this study, we analyze the sensitivities of ozone response to aerosol mixing states (e.g., mixing behaviour hypothesis of scattering and absorbing components) in the vertical direction and address the effects of aerosol-BL and aerosol-photolysis interactions on ozone profiles by WRF-Chem simulations. The aerosol internal mixing state experiment reasonably reproduces the vertical distribution and time variation of meteorological elements and ozone. Sensitive experiments show that aerosols lead to turbulent suppression, precursor accumulation, lower-level photolysis reduction and upper-level photolysis enhancement. Consequently, ozone basically decreases within entire BL during daytime (08:00~17:00), and the decrease is the least in external mixing state (0.6 %) compared with internal (9.8 %) and core-shell mixing states (7.4 %). The photolysis enhancement is the most significant in external mixing state due to its strong scattering ability. By process analysis, lower-level ozone chemical loss is enhanced due to photolysis reduction and NOX accumulation under VOC-limited regime. Upper-level ozone chemical production is accelerated due to higher photolysis rate resulting from aerosol backscattering. Therefore, the increased ozone entrainment from aloft BL to surface induced by boosted ozone vertical gradient outweighs the decreased ozone entrainment induced by turbulent suppression after 11:00 am. Additional simulations support that aerosol effect on precursor, photolysis and ozone is consistent under different underlying surface and pollution conditions.
Shuqi Yan et al.
Status: final response (author comments only)
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RC1: 'Comment on acp-2022-752', Anonymous Referee #1, 30 Nov 2022
- AC1: 'Reply on RC1', Shuqi Yan, 25 Feb 2023
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RC2: 'Comment on acp-2022-752', Anonymous Referee #2, 03 Jan 2023
This paper presents the results of impact of aerosol optics on vertical distribution of ozone. The authors reveal the characteristic of aerosol-BL and aerosol-photolysis interactions in different aerosol mixing states and their impacts on ozone variation. The general conclusion was that aerosols lead to turbulent suppression, precursor accumulation, lower-level photolysis reduction and upper-level photolysis enhancement. Additional simulations supported that aerosol effect on precursor, photolysis and ozone is consistent under different underlying surface and pollution conditions. The research topic fits into the ACP scope, and the paper was concisely written, I suggest this article be published with a minor revision.
General comments:
More discussions are needed to clarify the meaning and limitations of this research. This is important for other researchers to consider the applicability of this study. Observations from the field campaign can be included to support the results concluded from model simulations. In addition, I suggest modifying the titles of section 3.2, 3.3 and 3.4 to convey the main topic of each section more clearly.
On top of the above comments, the authors are also expected to address the following specific points:
Line 76-78: “We mainly use the data from 2 to 5 November to study the effect of aerosols on ozone, and detailly investigate the physical and chemical mechanisms in the pollution stage on 2 November”. I can not find related results in the manuscript.
Line 88: Which year’s emission inventory was used in this study?
Section 3.2: I’m confused about the content in this section. Why did you just describe the changes of NOx affected by aerosol-BL interactions instead of Ozone and PM2.5.
Line 161-162: Does ozone here mean that in BL?
Line 163: Should be “a strong positive gradient”.
Section 3.4: Discussions about the differences between three aerosol mixing states in process analysis are rare, I suggest adding some content to explain the differences described in the first paragraph.
Citation: https://doi.org/10.5194/acp-2022-752-RC2 - AC2: 'Reply on RC2', Shuqi Yan, 25 Feb 2023
Shuqi Yan et al.
Shuqi Yan et al.
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