the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Measurement Report: Spatial and vertical variability of aerosol optical properties during MOABAI mobile on-road campaign in North China Plain
Abstract. The North China Plain (NCP) has been experiencing serious air quality problems since the rapid urbanization and industrialization and has been the subject of many studies over the years. This work presents mapping at a fine scale of the aerosol spatial and vertical variability obtained during the MOABAI campaign (Mobile Observation of Atmosphere By vehicle-borne Aerosol measurement Instruments) using a van equipped with a micro-pulse LIDAR, a sun photometer and in situ instruments, performing on-road measurements. The campaign was conducted from 5 May to 23 May 2017 and had as a main objective to map the pollutants distribution in Beijing and NCP area. A summary of aerosol properties during all measurement days and a comprehensive case study along the industrial Binhai New Area near Tianjin are presented. The highest AOD at 440 nm (1.34 and 1.9) were recorded during two heavy pollution episodes on 18 May and 19 May 2017, respectively. The lowest PBL (Planetary Boundary Layer) heights (< 1500 m) were recorded during the heavy pollution events, correlated with the highest AOD. Transport of dust from Gobi Desert was captured during the mobile measurements, impacting Beijing in the 9–13 May period. Exploring the NCP outside Beijing provided datasets in regions with lack of aerosol observation sites and allowed mapping higher aerosol concentrations when passing by polluted cities in NCP (Baoding, Tianjin and Tangshan). In this study, we provide the first mass concentration profiles derived from a mobile micro-pulse LIDAR, making use of complementary information on aerosol type from sun photometer and in situ data. The case study of 17 May 2017 revealed mean extinction coefficients of 0.14 ± 0.10 km−1 at 532 nm and total mass concentration of 80 ± 62 μg m−3 in the PBL (< 2000 m) for the mobile transect from Tianjin to Tangshan along the coast of Bohai Sea. The highest extinction (0.56 km−1) and mass concentrations (404 μg m−3) were found in the industrial Binhai New Area. The PM10 and PM2.5 fractions of the total mass concentration profiles were separated using the columnar size distribution derived from sun photometer measurements. A general good agreement was found between the lidar-derived PM concentrations at surface level and the ones recorded at the closest air quality stations along the transect, with the only exception along the industrial region near Tianjin port, where emissions were highly variable.
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Interactive discussion
Status: closed
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RC1: 'Comment on acp-2020-1269', Anonymous Referee #3, 21 May 2021
This paper shows the observed results using the lidar, sunphotometer, and in-situ equipment mounted on a mobile vehicle. The main content is the analysis of observations in Beijing and NCP, where air pollution is the most common in China. Judging by the overall content, it is judged that it is unreasonable for this thesis to be published on the ACP in its current state.
Major Comments
- First, there seems to be no new scientific results in this paper. It is judged that the area to be observed has already been made a number of observations and researches and has not produced new analysis results.
- Second, what is judged as a new study result is a method of calculating the mass concentrations of PM10 and PM2.5 from the results of LiDAR data. However, this part does not appear to be written as a representation of the paper as a part of the whole paper.
In addition, the proposed method is a method that must have sunphotometer data, so it is judged that the expansion of future application will be limited.
Therefore, it is judged that there are many parts that are insufficient for this paper to be published in this journal at the current state. In order to be published in this journal, it is judged that a new paper should be written centering on the results of new scientific research.
Technical comments;
- line 49: Does “a negative trend” mean “decreasing trend of PM2.5? If correct, these expressions are likely to be interpreted in the opposite way when readers read them. Please correct it as it can be interpreted as an increase in the concentration of PM2.5.
line 119: How did you correct the wind direction/wind speed data measured by the weather station installed on a vehicle running at 90 km/h? There is no mention of that part in the text.
Citation: https://doi.org/10.5194/acp-2020-1269-RC1 - First, there seems to be no new scientific results in this paper. It is judged that the area to be observed has already been made a number of observations and researches and has not produced new analysis results.
-
RC2: 'Comment on acp-2020-1269', Anonymous Referee #1, 01 Jun 2021
This paper reports spatial and vertical distribution of optical and microphysical properties of aerosols derived from mobile vehicle measurements using a lidar, a sun-photometer, and in-situ instruments in the NCP, China during the MOABAI campaign (5 May to 23 May 2017). The observation using a vehicle and its data analysis are carried out based on the reliable methods established in the previous studies. On the other hand, new findings regarding the analysis results are unclear in this paper, and it is not enough as the “substantial new results” required for the “Measurement Report”. Therefore, a significant improvement in this point is necessary and it is not recommended to be published at this time.
Major Comments
- What are the new findings in this paper compared to previous aerosol observation studies in the NCP region?
- What are the characteristics of aerosols (spatial variability of optical properties, etc.) that cloud not be obtained by conventional fixed-point observations but could be obtained only by conducting vehicle observations in this research? For example, Fig. 2 can be a diagram that clearly shows the feature of this study, but the discussion in Section 3.1.1 described about it seems to be something that can be stated from the results of fixed-point observations.
Specific comments
- Fig. 4: In this figure, the place (close to or far from the sea) seems to be more important information than the time. Therefore, it is helpful for the readers to describe the location over time in Figs. (a) and (b) (e.g., 9:00-9:30 in Area A, 9:30-10:00 Area B, etc.)
- Section 3. 2.2 discusses the three peaks seen in fine mode. This peak is seen on the inland side (e.g., 9:00-9:30) and on the coast side (e.g., 12:30-13:00) for exactly the same particle size. It seems that the peak will change if the area changes, but is this reasonable?
- Line 334: “which shows that the two major aerosol contributions in the fine mode were sulphate and black carbon and nitrates in the coarse mode.” In this paper, there are no observations regarding the chemical composition, and previous studies are referred to. Therefore, it is definitive but an analogy. Therefore, “which implies” rather than “which shows” is considered valid.
- Conclusion: The findings obtained in this observational study should be clearly stated.
Citation: https://doi.org/10.5194/acp-2020-1269-RC2
Interactive discussion
Status: closed
-
RC1: 'Comment on acp-2020-1269', Anonymous Referee #3, 21 May 2021
This paper shows the observed results using the lidar, sunphotometer, and in-situ equipment mounted on a mobile vehicle. The main content is the analysis of observations in Beijing and NCP, where air pollution is the most common in China. Judging by the overall content, it is judged that it is unreasonable for this thesis to be published on the ACP in its current state.
Major Comments
- First, there seems to be no new scientific results in this paper. It is judged that the area to be observed has already been made a number of observations and researches and has not produced new analysis results.
- Second, what is judged as a new study result is a method of calculating the mass concentrations of PM10 and PM2.5 from the results of LiDAR data. However, this part does not appear to be written as a representation of the paper as a part of the whole paper.
In addition, the proposed method is a method that must have sunphotometer data, so it is judged that the expansion of future application will be limited.
Therefore, it is judged that there are many parts that are insufficient for this paper to be published in this journal at the current state. In order to be published in this journal, it is judged that a new paper should be written centering on the results of new scientific research.
Technical comments;
- line 49: Does “a negative trend” mean “decreasing trend of PM2.5? If correct, these expressions are likely to be interpreted in the opposite way when readers read them. Please correct it as it can be interpreted as an increase in the concentration of PM2.5.
line 119: How did you correct the wind direction/wind speed data measured by the weather station installed on a vehicle running at 90 km/h? There is no mention of that part in the text.
Citation: https://doi.org/10.5194/acp-2020-1269-RC1 - First, there seems to be no new scientific results in this paper. It is judged that the area to be observed has already been made a number of observations and researches and has not produced new analysis results.
-
RC2: 'Comment on acp-2020-1269', Anonymous Referee #1, 01 Jun 2021
This paper reports spatial and vertical distribution of optical and microphysical properties of aerosols derived from mobile vehicle measurements using a lidar, a sun-photometer, and in-situ instruments in the NCP, China during the MOABAI campaign (5 May to 23 May 2017). The observation using a vehicle and its data analysis are carried out based on the reliable methods established in the previous studies. On the other hand, new findings regarding the analysis results are unclear in this paper, and it is not enough as the “substantial new results” required for the “Measurement Report”. Therefore, a significant improvement in this point is necessary and it is not recommended to be published at this time.
Major Comments
- What are the new findings in this paper compared to previous aerosol observation studies in the NCP region?
- What are the characteristics of aerosols (spatial variability of optical properties, etc.) that cloud not be obtained by conventional fixed-point observations but could be obtained only by conducting vehicle observations in this research? For example, Fig. 2 can be a diagram that clearly shows the feature of this study, but the discussion in Section 3.1.1 described about it seems to be something that can be stated from the results of fixed-point observations.
Specific comments
- Fig. 4: In this figure, the place (close to or far from the sea) seems to be more important information than the time. Therefore, it is helpful for the readers to describe the location over time in Figs. (a) and (b) (e.g., 9:00-9:30 in Area A, 9:30-10:00 Area B, etc.)
- Section 3. 2.2 discusses the three peaks seen in fine mode. This peak is seen on the inland side (e.g., 9:00-9:30) and on the coast side (e.g., 12:30-13:00) for exactly the same particle size. It seems that the peak will change if the area changes, but is this reasonable?
- Line 334: “which shows that the two major aerosol contributions in the fine mode were sulphate and black carbon and nitrates in the coarse mode.” In this paper, there are no observations regarding the chemical composition, and previous studies are referred to. Therefore, it is definitive but an analogy. Therefore, “which implies” rather than “which shows” is considered valid.
- Conclusion: The findings obtained in this observational study should be clearly stated.
Citation: https://doi.org/10.5194/acp-2020-1269-RC2
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