the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Changes in surface ozone in South Korea on diurnal to decadal time scale for the period of 2001–2021
Kyoung-Min Kim
Yujoo Jeong
Seunghwan Seo
Yeonsu Park
Jeongyeon Kim
Abstract. Increasing trends of tropospheric ozone in South Korea in the last decades have reported in several studies, based on various metrics. In this study, we derived the trends of surface ozone in South Korea utilizing the daily maximum 8-hours average ozone concentrations (MDA8) measured at the surface from 2001 to 2021 and analyzed diurnal, seasonal, multi-decadal variations of this parameter at city, province, and background sites. The 4th highest MDA8 values have positive trends at 7 cities and 8 provinces throughout 2001–2021 with approximately 1–2 ppb yr-1 and were greater than 70 ppb after early 2010 for all sites, despite decreases of its precursor NO2 and CO. The Seoul Metropolitan Area (SMA) and the background sites have different diurnal and seasonal characteristics of MDA8 exceedances defined in this study (percentage of the data points with MDA8 > 70 ppb among all data points). SMA have much higher exceedances during summer than spring, while the background sites have much higher exceedances during spring than summer highlighting efficient local production of ozone in SMA during summer and strong influence of long-range transport during spring. The exceedances during spring and summer are similar for the rest of sites. The peaks of exceedances occur at 4–5 PM in SMA and most of locations, while exceedances mainly occur at 7–8 PM through night at the background sites. During spring of the COVID-19 pandemic (2020–2021), the MDA8 ozone exceedances decreased for most of locations with large NOx reductions in South Korea and China compared to 2010–2019. The large decreases of the MDA8 ozone exceedances occur in particular at the background sites during spring. In Gosung, Gangwondo (~600 m above sea level), the exceedances drop to ~5 % from 30 % in springtime during the COVID-19 pandemic. The concept of decreases of ozone in the boundary layer in Seoul and Gangwon-do to reductions in the emissions was confirmed by regional model simulations. The reductions of ozone exceedances did not occur at the major cities and provinces during summer of the COVID-19 pandemic with much smaller decreases of NOx in South Korea and China compared to spring. This study demonstrates distinctions between spring and summer in the formation and transport of surface ozone in South Korea and the need of monitoring and modeling with focus on different processes in each season or a finer time scale.
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Si-Wan Kim et al.
Status: closed
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RC1: 'Comment on acp-2022-788', Anonymous Referee #1, 02 Feb 2023
Review of “Changes in surface ozone in South Korea on diurnal to decadal time scale for the period of 2001-2021” by Kim et al.
This manuscript addressed an issue of observed surface ozone increases in South Korea by analyzing a long-term dataset and 3-d air quality model simulations for divulging its attribution. The surface ozone increase in South Korea and China is a compelling issue for which previous literature extensively attempted to investigate its causes. Compared to them, I find it quite challenging that this work shows a new contribution to the scientific understanding of the issue or a new idea that needs to be investigated in the future. In addition, the manuscript should be reshaped to highlight its main findings by adding descriptions of how the authors reached conclusions, which were mostly based on immature analyses. I will elaborate on them below.
P2,L2 - “Increasing trends of tropospheric ozone in South Korea” is a bit misleading because ozone in surface air does not always reflect tropospheric ozone. Needs to be revised to surface ozone.
P4,L11 - Here and elsewhere, references at not in the reference section. Please check all the citations and include other previous studies on the same issue (e.g., Colombi et al., ACPD, 2022, and the references are therein).
P4,L11 - “Ozone in South Korea …” this sentence requires a citation.
P8,L11 - Stratospheric ozone appears to have a significant effect on ozone in the troposphere and even in surface air in this study. However, I cannot find out how the effect of stratospheric ozone on tropospheric and surface ozone was quantified in the manuscript. I think that it should be elaborated on here.
Sections 2.4, 2.5. – This study used model simulations to understand the observed characteristics of surface ozone in South Korea. Therefore, an extensive model evaluation should be conducted and discussed somewhere in the manuscript by focusing on how good the model is to reproduce the observations and their variability.
P9,L4 – Years for the WRF-Chem simulations were missing. Did you conduct simulations for all years or for a particular year?
P9,L7 – It appears that the authors used different meteorology to drive CAM-Chem simulations and WRF-Chem simulations. Have you ever thought about using identical meteorology for both models?
P9,L14 – The time information of emissions inventory used in the model is missing. Did you also consider biomass burning emissions in the model?
P10,L9, - You analyzed the 4th highest MDA8 O3. I wonder how this metric well represents ozone air quality because these could be rather extreme events, which rarely happen. In other words, how frequently people in South Korea were exposed to this metric?
P10,L14 – The trend in Jeollanam-do differs from other provinces. This is explained by “MDA8O3 in Jeollanam-do is high before 2010”. I do not understand why this is the case. Here and elsewhere, please check out the proper usage of provinces and city names.
P10,L15-17 – This sentence includes several factors, contributing to ozone increases in South Korea. Proper citations are required.
P11,L2 – “Investigating seasonal differences in ozone in South Korea” has been examined by Lee and Park (2022). Any consistency or dissimilarity from the previous study is worth being mentioned.
P13,L1-13 – Stratospheric influences are quite large, which are still debatable. As I mentioned above, how did you obtain the stratospheric ozone influences on low tropospheric and surface ozone concentrations in South Korea? Does the model reproduce observations well? You have to elaborate a lot on this part.
P13,L14-20 – Colombi et al. (2022) already performed a nice analysis on the effect of precursor changes on observed surface ozone increases in South Korea. You have to compare your work with theirs.
P14,L6-20 – Previous studies published the observed increase in ozone in China and South Korea during the pandemic due to less titration of NOx. This result is contrary to previous studies and please compare the differences between this and previous work.
Section 4. You presented simulated vertical profiles in Seoul and Gangwondo during the KORUS-AQ. Could you include aircraft observations in Figure 11? I also wonder how the model simulates surface ozone concentrations.
Citation: https://doi.org/10.5194/acp-2022-788-RC1 -
AC1: 'Reply on RC1', Si-Wan Kim, 05 Apr 2023
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-788/acp-2022-788-AC1-supplement.pdf
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AC1: 'Reply on RC1', Si-Wan Kim, 05 Apr 2023
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RC2: 'Comment on acp-2022-788', Anonymous Referee #2, 21 Mar 2023
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-788/acp-2022-788-RC2-supplement.pdf
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AC2: 'Reply on RC2', Si-Wan Kim, 05 Jun 2023
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-788/acp-2022-788-AC2-supplement.pdf
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AC2: 'Reply on RC2', Si-Wan Kim, 05 Jun 2023
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RC3: 'Comment on acp-2022-788', Anonymous Referee #3, 05 Apr 2023
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AC3: 'Reply on RC3', Si-Wan Kim, 05 Jun 2023
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-788/acp-2022-788-AC3-supplement.pdf
-
AC3: 'Reply on RC3', Si-Wan Kim, 05 Jun 2023
Status: closed
-
RC1: 'Comment on acp-2022-788', Anonymous Referee #1, 02 Feb 2023
Review of “Changes in surface ozone in South Korea on diurnal to decadal time scale for the period of 2001-2021” by Kim et al.
This manuscript addressed an issue of observed surface ozone increases in South Korea by analyzing a long-term dataset and 3-d air quality model simulations for divulging its attribution. The surface ozone increase in South Korea and China is a compelling issue for which previous literature extensively attempted to investigate its causes. Compared to them, I find it quite challenging that this work shows a new contribution to the scientific understanding of the issue or a new idea that needs to be investigated in the future. In addition, the manuscript should be reshaped to highlight its main findings by adding descriptions of how the authors reached conclusions, which were mostly based on immature analyses. I will elaborate on them below.
P2,L2 - “Increasing trends of tropospheric ozone in South Korea” is a bit misleading because ozone in surface air does not always reflect tropospheric ozone. Needs to be revised to surface ozone.
P4,L11 - Here and elsewhere, references at not in the reference section. Please check all the citations and include other previous studies on the same issue (e.g., Colombi et al., ACPD, 2022, and the references are therein).
P4,L11 - “Ozone in South Korea …” this sentence requires a citation.
P8,L11 - Stratospheric ozone appears to have a significant effect on ozone in the troposphere and even in surface air in this study. However, I cannot find out how the effect of stratospheric ozone on tropospheric and surface ozone was quantified in the manuscript. I think that it should be elaborated on here.
Sections 2.4, 2.5. – This study used model simulations to understand the observed characteristics of surface ozone in South Korea. Therefore, an extensive model evaluation should be conducted and discussed somewhere in the manuscript by focusing on how good the model is to reproduce the observations and their variability.
P9,L4 – Years for the WRF-Chem simulations were missing. Did you conduct simulations for all years or for a particular year?
P9,L7 – It appears that the authors used different meteorology to drive CAM-Chem simulations and WRF-Chem simulations. Have you ever thought about using identical meteorology for both models?
P9,L14 – The time information of emissions inventory used in the model is missing. Did you also consider biomass burning emissions in the model?
P10,L9, - You analyzed the 4th highest MDA8 O3. I wonder how this metric well represents ozone air quality because these could be rather extreme events, which rarely happen. In other words, how frequently people in South Korea were exposed to this metric?
P10,L14 – The trend in Jeollanam-do differs from other provinces. This is explained by “MDA8O3 in Jeollanam-do is high before 2010”. I do not understand why this is the case. Here and elsewhere, please check out the proper usage of provinces and city names.
P10,L15-17 – This sentence includes several factors, contributing to ozone increases in South Korea. Proper citations are required.
P11,L2 – “Investigating seasonal differences in ozone in South Korea” has been examined by Lee and Park (2022). Any consistency or dissimilarity from the previous study is worth being mentioned.
P13,L1-13 – Stratospheric influences are quite large, which are still debatable. As I mentioned above, how did you obtain the stratospheric ozone influences on low tropospheric and surface ozone concentrations in South Korea? Does the model reproduce observations well? You have to elaborate a lot on this part.
P13,L14-20 – Colombi et al. (2022) already performed a nice analysis on the effect of precursor changes on observed surface ozone increases in South Korea. You have to compare your work with theirs.
P14,L6-20 – Previous studies published the observed increase in ozone in China and South Korea during the pandemic due to less titration of NOx. This result is contrary to previous studies and please compare the differences between this and previous work.
Section 4. You presented simulated vertical profiles in Seoul and Gangwondo during the KORUS-AQ. Could you include aircraft observations in Figure 11? I also wonder how the model simulates surface ozone concentrations.
Citation: https://doi.org/10.5194/acp-2022-788-RC1 -
AC1: 'Reply on RC1', Si-Wan Kim, 05 Apr 2023
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-788/acp-2022-788-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Si-Wan Kim, 05 Apr 2023
-
RC2: 'Comment on acp-2022-788', Anonymous Referee #2, 21 Mar 2023
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-788/acp-2022-788-RC2-supplement.pdf
-
AC2: 'Reply on RC2', Si-Wan Kim, 05 Jun 2023
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-788/acp-2022-788-AC2-supplement.pdf
-
AC2: 'Reply on RC2', Si-Wan Kim, 05 Jun 2023
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RC3: 'Comment on acp-2022-788', Anonymous Referee #3, 05 Apr 2023
-
AC3: 'Reply on RC3', Si-Wan Kim, 05 Jun 2023
The comment was uploaded in the form of a supplement: https://acp.copernicus.org/preprints/acp-2022-788/acp-2022-788-AC3-supplement.pdf
-
AC3: 'Reply on RC3', Si-Wan Kim, 05 Jun 2023
Si-Wan Kim et al.
Si-Wan Kim et al.
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