the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 22 May 2023
Climatological assessment of the vertically resolved optical and microphysical aerosol properties by lidar measurements, sunphotometer, and in-situ observations over 17 years at UPC Barcelona
Abstract. Aerosols are one of the most important pollutants in the atmosphere and have been monitored for the past few decades by both remote sensing and in situ observation platforms to assess the effectiveness of government-managed reduction emission policies and assess their impact on the radiative budget of the Earth's atmosphere. In fact, aerosols can directly modulate incoming short-wave solar radiation and outgoing long-wave radiation and indirectly influence cloud formation, lifetime, and precipitation. In this study, we quantitatively evaluated long-term temporal trends and seasonal variability from a climatological point of view of the optical and microphysical properties of atmospheric particulate matter at the Universitat Politècnica de Catalunya, Barcelona, Spain, over the past 17 years, through a synergy of lidar, sunphotometer, and in situ concentration measurements. Interannual temporal changes in aerosol optical and microphysical properties are evaluated through the seasonal Mann-Kendall test. Long-term trends in the optical depth of the recovered aerosol, the Ångström exponent (AE) and the concentrations of PM10, PM2.5 and PM1 reveal that emission reduction policies implemented in the last decades were effective in improving air quality, with consistent drops in PM concentrations and optical depth of aerosols. The seasonal analysis of the 17-year average vertically resolved aerosol profiles obtained from lidar observations shows that during summer the aerosol layer can be found up to an altitude of 5 km, after a sharp decay in the first km. In contrast, during the other seasons, the backscatter profiles fit a pronounced exponential decay well with a well-defined scale height. Long-range transport, especially dust outbreaks from the Sahara Desert, is likely to occur throughout the year. During winter, the dust aerosol layers are floating above the boundary layer, while during the other seasons they can penetrate the layer. This study sheds some light on meteorological processes and conditions that can lead to haze formation and helps decision makers adopt mitigation strategies to preserve large metropolitan areas in the Mediterranean basin.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(4597 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-893', Anonymous Referee #1, 30 Jun 2023
Review of “Climatological assessment of the vertically resolved optical and microphysical aerosol properties by lidar measurements, sunphotometer, and in-situ observations over 17 years at UPC Barcelona” by Lolli et al.
Large Picture:
This work introduces 17 years of observations of atmospheric aerosols using active observations from a ground-based lidar and passive observations using a ground-based sunphotometer. The significant length of this dataset allows for climatological interpretation to be made. Unlike satellite studies, the active nature of the lidar, and the high-quality nature of the sunphotometer allow for a signal to be more easily interpreted and quantified through the noise. This work then explores how there are significant impacts from biomass burning, dust, and other long-range transported sources. It shows clearly that there are both locally and long-range transported forcings which are present in the site studied. It also shows that while some of the observed changes are based more on season, that others are based on changes in the climate and/or anthropogenic emissions over the times being analyzed. Overall, the science is sound and the implications are clear. It is hoped that a bit more analysis can be added to address the influence of higher-frequency events, extreme events, and the possibility that May may be more like summer than spring in this region of the world. Some additional additions are recommended to strengthen the literature and background review. Overall, this is a worthy piece, which with a small amount of additional work, may yield one or two additional and stronger scientific findings.
Specific Details:
Line 50: Perhaps you can add some references and some comments to deepen the analysis with respect to the issue of emissions uncertainty. As pointed out, there has been a significant change in emissions due to the changes in human sources of aerosols since the start of the industrial revolution. However, there is a second and very important issue. The current databases of aerosol emissions is also highly uncertain, especially so for absorbing aerosols, such as biomass burning and dust, which are emphasized in this paper. For example, there are papers indicating that the emissions of absorbing aerosols inverted from remotely sensed observations can be 2 to 4 times higher than those from bottom-up approaches currently used by the IPCC and most modeling studies. Interestingly, these top-down inverted emissions studies tend to produce results which are more consistent with AERONET and LIDAR, and therefore should be far more closely aligned with the results from this paper. Such high-temporal-and-spatial constrained top-down emissions datasets may help aid in discovery of and attribution for extreme events and/or long-range transport, such as in the cases of wildfire and long-range transported mixed anthropogenic and dust source events which are analyzed in this work.
Line 165: Averaged Monthly and Seasonally? How many different higher frequency values of the Raman Lidar are there? Is there sufficient data that if the top less than 10% of events were analyzed separately, or if some other extreme analytical approaches were used, that it would be possible to detect high frequency changes? Again, this topic seems aligned with the overall results in this work, and may include a mixture of very intense but short-duration events such as fires, long-range transported pollution, and/or dust storms?
Line 190: Perhaps add in a sentence or two and additional details about how aerosols in the environment which are not locally source tend to be mixed. This is especially so for smaller sized particles (say under 2um), in which small carbon containing cores are slowly coated in-situ with organic and inorganic shells. There also are cases in which dust is coated with anthropogenic pollution observed in-situ. This could also be relevant for when collisions between dust and anthropogenic sources occur. Such analysis using a core/shell or other MIE based mixing approaches is already used by AERONET and therefore would yield a consistent result with your paper herein.
Line 200/201: While this is true, it also could be indicative of heavily aged anthropogenic or fire-based aerosol, which has been in the atmosphere for a very long time, and slowly grown in size to near the fine/coarse mode boundary.
Line 217: Using different metrics to weight the various independent wavelengths, it may also be possible to find out information about various mixed aerosol types.
Line 240: sensible?
Line 333: Other long-range transport of biomass burning papers as observed through multiple absorbing aerosol observations are available.
Line 346-348: Perhaps repeating the same analysis, but focusing on the 90th or 95th percentile of the data could yield additional interesting findings? The points made in this sentence could specifically be used to analyze if or how high pollution events are changing from a climatological perspective. Such a sensitivity test should be able to be done rapidly, while adding scientific value overall.
Figure 4: The MAM data has a flatter profile overall, and looks somewhat similar to the JJA data. If May were separated from MAM, would it look more like March and April, or more like JJA? Is it possible that the traditional division of seasons may not be the best way to analyze the groupings in this region of the world?
Lines 375-384: As mentioned above, the results from this paragraph with respect to transported BB may also be consistent with the May results being more similar to the JJA results than to the March and April results. Has this been checked?
Citation: https://doi.org/10.5194/egusphere-2023-893-RC1 -
AC1: 'Reply on RC1', Simone Lolli, 14 Aug 2023
Dear Reviewer,
Thank you for the comprehensive review and the constructive feedback on our manuscript. We appreciate the time and effort you took to understand and evaluate our work. We took into consideration all your comments. Below is a summary of our responses to the specific details you provided:
Line 50: We have added references and further elaborated on the issue of emissions uncertainty, specifically highlighting the difference in emissions from top-down and bottom-up approaches and their alignment with LIDAR and AERONET observations, as suggested.
Line 165 and lines 346-348: Thanks for your meaningful comment. We now provide details on the higher frequency values of the Raman Lidar. Additionally, we conducted the same analysis for the 95th. We added a picture and we found that the methodology is effective in detecting intense short-lived high pollution events, especially during the cold season. We found that there is an increase in intensity and frequency of Saharan dust outbreaks starting from 2016. We are going to further investigate those events, and we integrated the results into the text.
Line 190: We incorporated a discussion about the mixed nature of non-locally sourced aerosols, especially the smaller particles. The in-situ growth and core/shell mixing approaches consistent with AERONET have also been mentioned.
Line 200/201: Your observation is insightful. We have expanded our discussion to consider the possibility of aged anthropogenic or fire-based aerosols near the fine/coarse mode boundary.
Line 217: Based on your recommendation, we clarified this point and we added some more text.
Line 240: We have made necessary corrections for clarity.
Line 333: We have now included references to other research on long-range biomass burning observations, expanding the context and strengthening our claims.
Line 346-348: We re-analyzed our data focusing on the 95th percentile, as you suggested. The results from this analysis have enriched our findings and have been included in the revised version (see response for Line 165)
Figure 4: Based on your observation, we separated May data from MAM to compare it with March, April, and JJA. The results shed light on the seasonal discrepancies and have been discussed in the manuscript.
Lines 375-384: As suggested by the reviewer, we check if May is more similar to JJA. We found that this is effectively the case. Then May aligns closer to summer months than spring. We added a pragraph about that and we attached the plots for the reviewer in the supplement.
In summary, we believe that addressing these points has significantly strengthened our paper and made our findings more robust. We are grateful for your expert feedback, and we hope that our revisions make the manuscript worthy of publication.
-
AC1: 'Reply on RC1', Simone Lolli, 14 Aug 2023
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RC2: 'Comment on egusphere-2023-893', Anonymous Referee #3, 28 Jul 2023
This paper quantitatively evaluated long-term temporal trends and seasonal variability from a climatological point of view of the optical and microphysical properties of atmospheric particulate matter at the Universitat Politècnica de Catalunya, Barcelona, Spain, over the past 17 years, through a synergy of lidar, sunphotometer, and in situ concentration measurements. The topic is very interesting and has important climate and environment implications. The manuscript is well written and organized. While I found some minor issues need to be addressed before publish.
- All the number in PM10, PM2.5 and PM1 in the main text, tables and figures should be subscripted
- What is Lidar detection blind zone?
- Sens->Sen’s in figure 2a
- Brackets is not full in caption of table 4
- Color bar is missed in figure 5
- The present findings should be compared with previous studies.
Citation: https://doi.org/10.5194/egusphere-2023-893-RC2 -
AC2: 'Reply on RC2', Simone Lolli, 14 Aug 2023
We are very grateful to the reviewer for her/his time in reviewing the manuscript and for the positive comments. We have taken all the suggestions into account and incorporated them into the revised draft.
Citation: https://doi.org/10.5194/egusphere-2023-893-AC2
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-893', Anonymous Referee #1, 30 Jun 2023
Review of “Climatological assessment of the vertically resolved optical and microphysical aerosol properties by lidar measurements, sunphotometer, and in-situ observations over 17 years at UPC Barcelona” by Lolli et al.
Large Picture:
This work introduces 17 years of observations of atmospheric aerosols using active observations from a ground-based lidar and passive observations using a ground-based sunphotometer. The significant length of this dataset allows for climatological interpretation to be made. Unlike satellite studies, the active nature of the lidar, and the high-quality nature of the sunphotometer allow for a signal to be more easily interpreted and quantified through the noise. This work then explores how there are significant impacts from biomass burning, dust, and other long-range transported sources. It shows clearly that there are both locally and long-range transported forcings which are present in the site studied. It also shows that while some of the observed changes are based more on season, that others are based on changes in the climate and/or anthropogenic emissions over the times being analyzed. Overall, the science is sound and the implications are clear. It is hoped that a bit more analysis can be added to address the influence of higher-frequency events, extreme events, and the possibility that May may be more like summer than spring in this region of the world. Some additional additions are recommended to strengthen the literature and background review. Overall, this is a worthy piece, which with a small amount of additional work, may yield one or two additional and stronger scientific findings.
Specific Details:
Line 50: Perhaps you can add some references and some comments to deepen the analysis with respect to the issue of emissions uncertainty. As pointed out, there has been a significant change in emissions due to the changes in human sources of aerosols since the start of the industrial revolution. However, there is a second and very important issue. The current databases of aerosol emissions is also highly uncertain, especially so for absorbing aerosols, such as biomass burning and dust, which are emphasized in this paper. For example, there are papers indicating that the emissions of absorbing aerosols inverted from remotely sensed observations can be 2 to 4 times higher than those from bottom-up approaches currently used by the IPCC and most modeling studies. Interestingly, these top-down inverted emissions studies tend to produce results which are more consistent with AERONET and LIDAR, and therefore should be far more closely aligned with the results from this paper. Such high-temporal-and-spatial constrained top-down emissions datasets may help aid in discovery of and attribution for extreme events and/or long-range transport, such as in the cases of wildfire and long-range transported mixed anthropogenic and dust source events which are analyzed in this work.
Line 165: Averaged Monthly and Seasonally? How many different higher frequency values of the Raman Lidar are there? Is there sufficient data that if the top less than 10% of events were analyzed separately, or if some other extreme analytical approaches were used, that it would be possible to detect high frequency changes? Again, this topic seems aligned with the overall results in this work, and may include a mixture of very intense but short-duration events such as fires, long-range transported pollution, and/or dust storms?
Line 190: Perhaps add in a sentence or two and additional details about how aerosols in the environment which are not locally source tend to be mixed. This is especially so for smaller sized particles (say under 2um), in which small carbon containing cores are slowly coated in-situ with organic and inorganic shells. There also are cases in which dust is coated with anthropogenic pollution observed in-situ. This could also be relevant for when collisions between dust and anthropogenic sources occur. Such analysis using a core/shell or other MIE based mixing approaches is already used by AERONET and therefore would yield a consistent result with your paper herein.
Line 200/201: While this is true, it also could be indicative of heavily aged anthropogenic or fire-based aerosol, which has been in the atmosphere for a very long time, and slowly grown in size to near the fine/coarse mode boundary.
Line 217: Using different metrics to weight the various independent wavelengths, it may also be possible to find out information about various mixed aerosol types.
Line 240: sensible?
Line 333: Other long-range transport of biomass burning papers as observed through multiple absorbing aerosol observations are available.
Line 346-348: Perhaps repeating the same analysis, but focusing on the 90th or 95th percentile of the data could yield additional interesting findings? The points made in this sentence could specifically be used to analyze if or how high pollution events are changing from a climatological perspective. Such a sensitivity test should be able to be done rapidly, while adding scientific value overall.
Figure 4: The MAM data has a flatter profile overall, and looks somewhat similar to the JJA data. If May were separated from MAM, would it look more like March and April, or more like JJA? Is it possible that the traditional division of seasons may not be the best way to analyze the groupings in this region of the world?
Lines 375-384: As mentioned above, the results from this paragraph with respect to transported BB may also be consistent with the May results being more similar to the JJA results than to the March and April results. Has this been checked?
Citation: https://doi.org/10.5194/egusphere-2023-893-RC1 -
AC1: 'Reply on RC1', Simone Lolli, 14 Aug 2023
Dear Reviewer,
Thank you for the comprehensive review and the constructive feedback on our manuscript. We appreciate the time and effort you took to understand and evaluate our work. We took into consideration all your comments. Below is a summary of our responses to the specific details you provided:
Line 50: We have added references and further elaborated on the issue of emissions uncertainty, specifically highlighting the difference in emissions from top-down and bottom-up approaches and their alignment with LIDAR and AERONET observations, as suggested.
Line 165 and lines 346-348: Thanks for your meaningful comment. We now provide details on the higher frequency values of the Raman Lidar. Additionally, we conducted the same analysis for the 95th. We added a picture and we found that the methodology is effective in detecting intense short-lived high pollution events, especially during the cold season. We found that there is an increase in intensity and frequency of Saharan dust outbreaks starting from 2016. We are going to further investigate those events, and we integrated the results into the text.
Line 190: We incorporated a discussion about the mixed nature of non-locally sourced aerosols, especially the smaller particles. The in-situ growth and core/shell mixing approaches consistent with AERONET have also been mentioned.
Line 200/201: Your observation is insightful. We have expanded our discussion to consider the possibility of aged anthropogenic or fire-based aerosols near the fine/coarse mode boundary.
Line 217: Based on your recommendation, we clarified this point and we added some more text.
Line 240: We have made necessary corrections for clarity.
Line 333: We have now included references to other research on long-range biomass burning observations, expanding the context and strengthening our claims.
Line 346-348: We re-analyzed our data focusing on the 95th percentile, as you suggested. The results from this analysis have enriched our findings and have been included in the revised version (see response for Line 165)
Figure 4: Based on your observation, we separated May data from MAM to compare it with March, April, and JJA. The results shed light on the seasonal discrepancies and have been discussed in the manuscript.
Lines 375-384: As suggested by the reviewer, we check if May is more similar to JJA. We found that this is effectively the case. Then May aligns closer to summer months than spring. We added a pragraph about that and we attached the plots for the reviewer in the supplement.
In summary, we believe that addressing these points has significantly strengthened our paper and made our findings more robust. We are grateful for your expert feedback, and we hope that our revisions make the manuscript worthy of publication.
-
AC1: 'Reply on RC1', Simone Lolli, 14 Aug 2023
-
RC2: 'Comment on egusphere-2023-893', Anonymous Referee #3, 28 Jul 2023
This paper quantitatively evaluated long-term temporal trends and seasonal variability from a climatological point of view of the optical and microphysical properties of atmospheric particulate matter at the Universitat Politècnica de Catalunya, Barcelona, Spain, over the past 17 years, through a synergy of lidar, sunphotometer, and in situ concentration measurements. The topic is very interesting and has important climate and environment implications. The manuscript is well written and organized. While I found some minor issues need to be addressed before publish.
- All the number in PM10, PM2.5 and PM1 in the main text, tables and figures should be subscripted
- What is Lidar detection blind zone?
- Sens->Sen’s in figure 2a
- Brackets is not full in caption of table 4
- Color bar is missed in figure 5
- The present findings should be compared with previous studies.
Citation: https://doi.org/10.5194/egusphere-2023-893-RC2 -
AC2: 'Reply on RC2', Simone Lolli, 14 Aug 2023
We are very grateful to the reviewer for her/his time in reviewing the manuscript and for the positive comments. We have taken all the suggestions into account and incorporated them into the revised draft.
Citation: https://doi.org/10.5194/egusphere-2023-893-AC2
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Michaël Sicard
Francesco Amato
Adolfo Comeron
Cristina Gíl-Diaz
Tony C. Landi
Constantino Munoz-Porcar
Daniel Oliveira
Federico Dios Otin
Francesc Rocadenbosch
Alejandro Rodriguez-Gomez
Andrés Alastuey
Xavier Querol
Cristina Reche
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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