the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 26 Jun 2023
The influences of El Niño–Southern Oscillation on tropospheric ozone in CMIP6 models
Abstract. Ozone in the troposphere is a greenhouse gas and a pollutant, hence, additional understanding of the drivers of tropospheric ozone evolution is essential. The El Niño–Southern Oscillation (ENSO) is a main climate mode and may contribute to the variations of tropospheric ozone. Nevertheless, there is uncertainty regarding the causal influences of ENSO on tropospheric ozone under warming environment. Here, we investigated the links between ENSO and tropospheric ozone using Coupled Modeling Intercomparison Project Phase 6 (CMIP6) data over the period 1850–2014. Our results show that ENSO impacts on tropospheric ozone are primarily found over oceans, while the signature of ENSO over continents is largely nonsignificant. The response of ozone to ENSO may vary depending on specific air pressure levels in the troposphere. These responses are weak in the middle troposphere and are stronger in the upper and lower troposphere. Although there are biases in simulating the signature of ENSO on surface ozone, these signatures in the middle and upper troposphere appear to be more consistent across CMIP6 models. While the response of tropical tropospheric ozone to ENSO is in agreement with previous works, our results suggest that ENSO impacts on tropospheric ozone of the mid-latitude regions over the southern Pacific, Atlantic, and Indian oceans might be more significant than previously understood.
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RC1: 'Comment on egusphere-2023-207', Anonymous Referee #1, 11 Jul 2023
1. The Pacific decadal oscillation which is also one of the main climate mode that can affect
ENSO and indeed on the ozone concentrations. The authors didn’t explain why other
climate modes are not considered and
why only three (Dipole mode Index, Southern
Annual Mode and North Atlantic Oscillation) climate modes.
2. Try to elaborate mainly the common schemes in the Atmospheric Chemistry Modules
that are in the models (other than the three models BCC_CSM2_MR, IPSL_CM6A_LR
and MPI_ESM1_2_LR) as the behavior of these models in connection to the response of
ENSO on ozone variation is similar.3. The Text S1 which explains about the method that has been adopted should be mentioned
under the method section 2.2 rather than in the supplement. It helps the reader to have a
quick through of the methodology adopted in the study.
4. Why did you consider only 1000 hPa, 850 hPa, 500 hPa and 300 hPa ? Are these pressure
levels enough to represent the respective atmospheric region of the atmosphere (like
middle troposphere, upper troposphere). As ENSO is responsible for changes in winds
and circulation patterns. It is also expected to have impact on the transport of ozone from
the lower troposphere to upper troposphere and lower stratosphere. It would be
interesting if you can check if the features are same in the upper levels (above 300 hPa
just below the tropopause)Line Nos.:42:43: Did you check if the findings obtained using CMIP6 and CMIP5 ? If so where
did you find the changes that resulted in the current result?
Line Nos.: 51: The list of the models mentioned in Table S1 should be shifted to the main
manuscript instead of supplement.
Line Nos. 53:55: The authors are suggested to explain little more on the findings of the cited
papers rather than just citing the paper.
The Figures can be of more clarity (mainly the stippling in figures are not at all visible (for
example Figure 1 (a)) are not visible clearly, The titles in the Figure 3 should be made little big)- AC1: 'Reply on RC1', Thanh Le, 07 Dec 2023
-
RC2: 'Comment on egusphere-2023-207', Anonymous Referee #3, 13 Nov 2023
This study investigated the effect of ENSO on tropospheric ozone over the period 1850-2014, focusing on the 300, 500, 850 and 1000 hPa. The authors also used the probability for the absence of Granger causality from ENSO to ozone concentrations. The topic is interesting. However, before it can be considered for publication, some aspects need more explanation.
- My major concern is that can the current CMIP6 model simulations including the ozone chemistry and it related physical and chemical processes. For example, the first BCC model does not have atmospheric chemistry model (Table S1), how can it predict ozone? The No.3-6 are all CESM2 model. Do these model configurations predict tropospheric ozone with fully atmospheric chemistry? The MAM4 is the name of aerosol module not the atmospheric chemistry. Also, are the simulated ozone in these models evaluated? Some models cannot well reproduce the global distribution of ozone and some cannot characterize the response of ozone to ENSO signal shown in observations.
- The conclusions about the effect of ENSO on seasonal ozone in the troposphere can be added to the abstract.
- Line35-40: It is suggested to provide the details of the uncertainties regarding the causal effects of ENSO on global tropospheric ozone. Although the authors provided some references, the information from these references should be strengthened.
- The effect of ENSO on ozone in the lower troposphere is more significant than that in the upper and middle troposphere. Please elaborate the reason. Moreover, the models’ agreement is weak in reproducing ozone in the lower troposphere and the standard deviation is high in the tropics. In this context, is the conclusion that ENSO affects the lower troposphere in the tropics convincing?
- Line 116 “The significant impacts of ENSO on ozone … might be associated with the transport of ozone from east Asia”. If so, the effect of ENSO on ozone over east Asia should be found. But it doesn't. Can you add some explanation about it?
Citation: https://doi.org/10.5194/egusphere-2023-207-RC2 - AC2: 'Reply on RC2', Thanh Le, 07 Dec 2023
Status: closed
-
RC1: 'Comment on egusphere-2023-207', Anonymous Referee #1, 11 Jul 2023
1. The Pacific decadal oscillation which is also one of the main climate mode that can affect
ENSO and indeed on the ozone concentrations. The authors didn’t explain why other
climate modes are not considered and
why only three (Dipole mode Index, Southern
Annual Mode and North Atlantic Oscillation) climate modes.
2. Try to elaborate mainly the common schemes in the Atmospheric Chemistry Modules
that are in the models (other than the three models BCC_CSM2_MR, IPSL_CM6A_LR
and MPI_ESM1_2_LR) as the behavior of these models in connection to the response of
ENSO on ozone variation is similar.3. The Text S1 which explains about the method that has been adopted should be mentioned
under the method section 2.2 rather than in the supplement. It helps the reader to have a
quick through of the methodology adopted in the study.
4. Why did you consider only 1000 hPa, 850 hPa, 500 hPa and 300 hPa ? Are these pressure
levels enough to represent the respective atmospheric region of the atmosphere (like
middle troposphere, upper troposphere). As ENSO is responsible for changes in winds
and circulation patterns. It is also expected to have impact on the transport of ozone from
the lower troposphere to upper troposphere and lower stratosphere. It would be
interesting if you can check if the features are same in the upper levels (above 300 hPa
just below the tropopause)Line Nos.:42:43: Did you check if the findings obtained using CMIP6 and CMIP5 ? If so where
did you find the changes that resulted in the current result?
Line Nos.: 51: The list of the models mentioned in Table S1 should be shifted to the main
manuscript instead of supplement.
Line Nos. 53:55: The authors are suggested to explain little more on the findings of the cited
papers rather than just citing the paper.
The Figures can be of more clarity (mainly the stippling in figures are not at all visible (for
example Figure 1 (a)) are not visible clearly, The titles in the Figure 3 should be made little big)- AC1: 'Reply on RC1', Thanh Le, 07 Dec 2023
-
RC2: 'Comment on egusphere-2023-207', Anonymous Referee #3, 13 Nov 2023
This study investigated the effect of ENSO on tropospheric ozone over the period 1850-2014, focusing on the 300, 500, 850 and 1000 hPa. The authors also used the probability for the absence of Granger causality from ENSO to ozone concentrations. The topic is interesting. However, before it can be considered for publication, some aspects need more explanation.
- My major concern is that can the current CMIP6 model simulations including the ozone chemistry and it related physical and chemical processes. For example, the first BCC model does not have atmospheric chemistry model (Table S1), how can it predict ozone? The No.3-6 are all CESM2 model. Do these model configurations predict tropospheric ozone with fully atmospheric chemistry? The MAM4 is the name of aerosol module not the atmospheric chemistry. Also, are the simulated ozone in these models evaluated? Some models cannot well reproduce the global distribution of ozone and some cannot characterize the response of ozone to ENSO signal shown in observations.
- The conclusions about the effect of ENSO on seasonal ozone in the troposphere can be added to the abstract.
- Line35-40: It is suggested to provide the details of the uncertainties regarding the causal effects of ENSO on global tropospheric ozone. Although the authors provided some references, the information from these references should be strengthened.
- The effect of ENSO on ozone in the lower troposphere is more significant than that in the upper and middle troposphere. Please elaborate the reason. Moreover, the models’ agreement is weak in reproducing ozone in the lower troposphere and the standard deviation is high in the tropics. In this context, is the conclusion that ENSO affects the lower troposphere in the tropics convincing?
- Line 116 “The significant impacts of ENSO on ozone … might be associated with the transport of ozone from east Asia”. If so, the effect of ENSO on ozone over east Asia should be found. But it doesn't. Can you add some explanation about it?
Citation: https://doi.org/10.5194/egusphere-2023-207-RC2 - AC2: 'Reply on RC2', Thanh Le, 07 Dec 2023
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