the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Air quality observations onboard commercial and targeted Zeppelin flights in Germany – a platform for high-resolution trace-gas and aerosol measurements within the planetary boundary layer
- 1Institute of Energy and Climate Research, IEK-8: Troposphere, Forschungszentrum Jülich GmbH, Jülich, Germany
- 2MIRO Analytical AG, Wallisellen, 8304, Switzerland
- 1Institute of Energy and Climate Research, IEK-8: Troposphere, Forschungszentrum Jülich GmbH, Jülich, Germany
- 2MIRO Analytical AG, Wallisellen, 8304, Switzerland
Abstract. A Zeppelin airship was used as a platform for in-situ measurements of greenhouse gases and short-lived air pollutants within the planetary boundary layer in Germany. A novel quantum cascade laser-based multi-compound gas analyzer (MIRO Analytical AG) was deployed to simultaneously measure in-situ concentrations of greenhouse gases (CO2, N2O, H2O, and CH4) and air pollutants (CO, NO, NO2, O3, SO2, and NH3) with high precision at a measurement rate of 1 Hz. These measurements were complemented by electrochemical sensors for NO, NO2, Ox (NO2+O3), and CO, an optical particle counter, temperature, humidity, altitude, and position monitoring. Instruments were operated remotely without the need for on-site interactions. Three two-week campaigns were conducted in 2020 comprising commercial passenger as well as targeted flights over multiple German cities including Cologne, Mönchengladbach, Düsseldorf, Aachen, Frankfurt, but also over industrial areas and highways.
Vertical profiles of trace gases were obtained during the airship landing and take-off. Diurnal variability of the Zeppelin vertical profiles was compared to measurements from ground-based monitoring stations with a focus on nitrogen oxides and ozone. We find that their variability can be explained by the increasing nocturnal boundary layer height from early morning towards midday, an increase in emissions during rush hour traffic, and the rapid photochemical activity midday. Higher altitude (250–450 m) NOX to CO ratios are further compared to the 2015 EDGAR emission inventory to find that pollutant concentrations are influenced by transportation and residential emissions as well as manufacturing industries and construction activity. Finally, we report NOx and CO concentrations from one plume transect originating from a coal power plant and compare it to the EURAD-IM model to find agreement within 15 %. However, due to the increased contribution of solar and wind energy and/or the impact of lockdown measures the power plant was operated at max. 50 % capacity; therefore, possible overestimation of emissions by the model cannot be excluded.
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Ralf Tillmannn et al.
Status: closed
-
RC1: 'Comment on amt-2021-360', Anonymous Referee #1, 03 Dec 2021
Tillmann et al. present observations of greenhouse gases and important primary and secondary pollutants that impact air quality. These measurements were condutcted on a Zeppelin, allowing for both targeted measurements as well as measurements conducted at lower altitudes than typical for aircraft. With the observations, the authors were able to show the collapse of the nocturnal residual layer and the mixing of the boundary layer with the residual layer, some investigation into emission sources, and comparisons of emissions/transport with a model for selected sources.
Though the paper is of interest and provides valuable results/information, currently as presented, the paper seems to be more geared for Atmospheric Chemistry and Physics and not Atmospheric Measurement Technique. The reasoning behind that is discussed in more detail below. Further, there are areas where further clarification and discussion about the methodology is needed. Depending on what direction the authors decide to take will make this paper either acceptable for AMT or ACP.
As this was submitted to a measurement technique journal, it would be expected that more details would be included concerning the measurement and techniques. However, the authors provide minimal information about the measurement techniques. The following, at minimum, should be included to make this paper more appropriate for AMT:
1) Comparison of the low-cost sensors along with MIRO. Including, but not limited to, sensitivity, response times, interferences (including any potential RH or temperature dependencies, esp. if this unit is not in a temperature controlled area of the Zeppelin), any pressure dependencies, how limit of detection may change with integration time, etc.
2) Response time of MIRO, along with the lines used. This is especially important as:
a) MIRO is measuring sticky molecules (H2O and NH3) so how quickly can MIRO actually respond to entering/exiting boundary layer?
b) As one of the selling points of this package is that it can better characterize boundary layer, residual layer, and potentially free troposphere, the instrument quickly responding entering & exiting these different regimes is important. This can also have potential relative humidity dependencies that will be important to discuss and outline.3) Discussion of the sampling scheme--what is the tubing (type, internal diameter, length) from the inlet to the different instruments? What is the residence time? Is it heated? Similarly for the zero air supply?
4) What is the cooling system for? What is the zero air catridges for? What is the pressure controller for? What happens without these devices?
5) How reliable is this instrument on maintaining the lines/features to measure the compounds listed? How easy is it to get back to the lines/features if the instrument loses them due to pressure or temperature fluctations?
6) An important question that the authors brought up includes boundary layer and residual layer. Currently there are minimal measurements in the residual layer and in differentiating boundary layer, residual layer, and free troposphere. Is there an alogarithm from the observations the authors presented that they can estimate the heights of these levels?
The following clarifications/discussions would improve the paper:
1) It is currently unclear throughout Section 3 if the authors are only talking about MIRO or if it is a combination of MIRO and electrochemical sensors.
2) As a side note, since the authors brought up the electrochemical and optical measurements, at least a minor discussion of these measurements would be beneficial for this manuscript. Further, for the optical counter, what type of line (Teflon vs copper/stainless steel) and dryer used?
2) As geostationary satellites are coming on-line, a discussion in how this package could be used to validate the geostationary satellites would be of use. This is espeically important as the package includes many of the species that the satellites will be trying to target. How does the integrated column change between the different times the authors discuss, along with the air mass factor, between having a nocturnal residual layer and a well mixed boundary layer?
3) The purpose of Fig. 4 and the associated discussion is currently not clear. Numerous studies from NASA DISCOVER-AQ and KORUS-AQ have indicated that NOx is not well mixed between ground and at altitude measurements (e.g., Flynn et al., 2014; Flynn et al., 2016; Choi et al., 2020; Li et al., 2021). A discussion in how the profile from the ground-based observations and the Zeppelin profile may be more suitable.
4) Why does it take the NOx concentrations to be higher at 250 - 300 m longer than rest of the boundary layer? Does it make sense with mixing/collapse of the residual layer?
5) The authors mention that compounds need to have similar loss rates in order to do ratios to understand emission ratios/sources (Section 3.3). However, NO2 has a very short lifetime (shorter than the 7 - 11 hours the authors noted due to the production of peroxy acyl nitrates, PAN, and alkyl and multifunctional nitrates, e.g., Valin et al., 2013). The authors should show what the ratio of NOx to CO from ground monitoring sites are and compare with the Zeppelin measurements to (a) show confidence in the assumptions and ratios they provide and (b) what new information the Zeppelin provides that ground measurements currnetly may not provide.
Minor:
1) Please make sure to be consistent about underscoring the x in NOx.
2) Please recheck the grammar and capitilzation throughout the manuscript. E.g., World Health Organization is not capitalized and there are many instances were commas would be appropriate to separate a describer (e.g., line 50, "networks e.g. the European Environment Agency EEA together" should be "networks, e.g., the European Environment Agency, EEA, together"). Also, contractions (e.g., don't) should not be used.
3) It is generally recommended that references that use websites should have similar in-line references as papers in that the website reference is listed at the end in the references section.
4) Why is the evening rush hour for NOx at such a late time (~8:00-9:00 PM local time). I would expect the rush hour to be between 4:00 and 7:00 PM local time.
5) Fig. 4: why are some of the flight paths thicker?
6) Fig. 7: I would recommend the observations have a black outline as they are hard to see with the background model results.
-
RC2: 'Reply on RC1', Anonymous Referee #1, 03 Dec 2021
Forgot the references:
Choi et al. Assessment of NO2 observations during DISCOVER-AQ and KORUS-AQ field campaigns. https://doi.org/10.5194/amt-13-2523-2020. 2020.
Flynn et al. Relationship between column-density and surface mixing ratio: Statistical analysis of O3 and NO2 data from the July 2011 Maryland DISCOVER-AQ mission. AE. https://doi.org/10.1016/j.atmosenv.2014.04.041. 2014.
Flynn et al. Variability of O3 and NO2 profile shapes during DISCOVER-AQ: Implications for satellite observations and comparisons to model-simulated profiles. AE. https://doi.org/10.1016/j.atmosenv.2016.09.068. 2016.
Li et al. Comprehensive evaluations of diurnal NO2 measurements during DISCOVER-AQ 2011: effects of resolution-dependent representation of NOx emissions. ACP. https://doi.org/10.5194/acp-21-11133-2021. 2021.
Valin et al. Variations of OH radical in an urban plume inferred from NO2 column measurements. GRL. https://doi.org/10.1002/grl.50267. 2013.
- AC3: 'Reply on RC2', Ralf Tillmann, 23 Feb 2022
- AC1: 'Reply on RC1', Ralf Tillmann, 22 Feb 2022
-
RC2: 'Reply on RC1', Anonymous Referee #1, 03 Dec 2021
-
RC3: 'Comment on amt-2021-360', Anonymous Referee #2, 27 Dec 2021
Tillmann et al. provide an overview of the utilization of a new Zeppelin research platform equipped with instrumentation for air quality studies. They provide some examples of the unique sampling strategies that can be provided with such a platform (i.e. details of the vertical structure of the boundary layer) and the use of the platform to evaluate an emissions inventory.
Generally I think that what is presented is well done. Since the paper is submitted to AMT, I was expecting some more details on the evaluation of the data quality from the different instruments onboard. As far as I can tell, the measurements presented are only from the MIRO instrument. I think it would be appropriate to have a section discussing the data quality from the less expensive chemical sensors, and comment on their utility for the future. Was the intention of integrating them along with the MIRO to evaluate them, or was it to possibly rely on those only in the future for this or other platforms?
On the MIRO side, not all of the chemical measurements were discussed. I think it would be good to comment on the SO2 and NH3 data quality, since these are important for air quality studies and the use of a single instrument capable of providing all of those measurement would be really of wide interest. As the manuscript is though, we don’t know if those measurements were deemed to be of sufficient quality for air quality research.
I think that it may be appropriate for a revised version of the paper to be published in AMT, but think that first the sections that deal with the instrumentation should be expanded a bit to:
- Provide some comments on the observed data quality or issues from the MIRO, for example how much did the zeros drift?
- Expand the data discussion to comment at least on the SO2 and NH3 measurement, and
- Compare the measurements between MIRO and the sensors.
- AC2: 'Reply on RC3', Ralf Tillmann, 22 Feb 2022
Status: closed
-
RC1: 'Comment on amt-2021-360', Anonymous Referee #1, 03 Dec 2021
Tillmann et al. present observations of greenhouse gases and important primary and secondary pollutants that impact air quality. These measurements were condutcted on a Zeppelin, allowing for both targeted measurements as well as measurements conducted at lower altitudes than typical for aircraft. With the observations, the authors were able to show the collapse of the nocturnal residual layer and the mixing of the boundary layer with the residual layer, some investigation into emission sources, and comparisons of emissions/transport with a model for selected sources.
Though the paper is of interest and provides valuable results/information, currently as presented, the paper seems to be more geared for Atmospheric Chemistry and Physics and not Atmospheric Measurement Technique. The reasoning behind that is discussed in more detail below. Further, there are areas where further clarification and discussion about the methodology is needed. Depending on what direction the authors decide to take will make this paper either acceptable for AMT or ACP.
As this was submitted to a measurement technique journal, it would be expected that more details would be included concerning the measurement and techniques. However, the authors provide minimal information about the measurement techniques. The following, at minimum, should be included to make this paper more appropriate for AMT:
1) Comparison of the low-cost sensors along with MIRO. Including, but not limited to, sensitivity, response times, interferences (including any potential RH or temperature dependencies, esp. if this unit is not in a temperature controlled area of the Zeppelin), any pressure dependencies, how limit of detection may change with integration time, etc.
2) Response time of MIRO, along with the lines used. This is especially important as:
a) MIRO is measuring sticky molecules (H2O and NH3) so how quickly can MIRO actually respond to entering/exiting boundary layer?
b) As one of the selling points of this package is that it can better characterize boundary layer, residual layer, and potentially free troposphere, the instrument quickly responding entering & exiting these different regimes is important. This can also have potential relative humidity dependencies that will be important to discuss and outline.3) Discussion of the sampling scheme--what is the tubing (type, internal diameter, length) from the inlet to the different instruments? What is the residence time? Is it heated? Similarly for the zero air supply?
4) What is the cooling system for? What is the zero air catridges for? What is the pressure controller for? What happens without these devices?
5) How reliable is this instrument on maintaining the lines/features to measure the compounds listed? How easy is it to get back to the lines/features if the instrument loses them due to pressure or temperature fluctations?
6) An important question that the authors brought up includes boundary layer and residual layer. Currently there are minimal measurements in the residual layer and in differentiating boundary layer, residual layer, and free troposphere. Is there an alogarithm from the observations the authors presented that they can estimate the heights of these levels?
The following clarifications/discussions would improve the paper:
1) It is currently unclear throughout Section 3 if the authors are only talking about MIRO or if it is a combination of MIRO and electrochemical sensors.
2) As a side note, since the authors brought up the electrochemical and optical measurements, at least a minor discussion of these measurements would be beneficial for this manuscript. Further, for the optical counter, what type of line (Teflon vs copper/stainless steel) and dryer used?
2) As geostationary satellites are coming on-line, a discussion in how this package could be used to validate the geostationary satellites would be of use. This is espeically important as the package includes many of the species that the satellites will be trying to target. How does the integrated column change between the different times the authors discuss, along with the air mass factor, between having a nocturnal residual layer and a well mixed boundary layer?
3) The purpose of Fig. 4 and the associated discussion is currently not clear. Numerous studies from NASA DISCOVER-AQ and KORUS-AQ have indicated that NOx is not well mixed between ground and at altitude measurements (e.g., Flynn et al., 2014; Flynn et al., 2016; Choi et al., 2020; Li et al., 2021). A discussion in how the profile from the ground-based observations and the Zeppelin profile may be more suitable.
4) Why does it take the NOx concentrations to be higher at 250 - 300 m longer than rest of the boundary layer? Does it make sense with mixing/collapse of the residual layer?
5) The authors mention that compounds need to have similar loss rates in order to do ratios to understand emission ratios/sources (Section 3.3). However, NO2 has a very short lifetime (shorter than the 7 - 11 hours the authors noted due to the production of peroxy acyl nitrates, PAN, and alkyl and multifunctional nitrates, e.g., Valin et al., 2013). The authors should show what the ratio of NOx to CO from ground monitoring sites are and compare with the Zeppelin measurements to (a) show confidence in the assumptions and ratios they provide and (b) what new information the Zeppelin provides that ground measurements currnetly may not provide.
Minor:
1) Please make sure to be consistent about underscoring the x in NOx.
2) Please recheck the grammar and capitilzation throughout the manuscript. E.g., World Health Organization is not capitalized and there are many instances were commas would be appropriate to separate a describer (e.g., line 50, "networks e.g. the European Environment Agency EEA together" should be "networks, e.g., the European Environment Agency, EEA, together"). Also, contractions (e.g., don't) should not be used.
3) It is generally recommended that references that use websites should have similar in-line references as papers in that the website reference is listed at the end in the references section.
4) Why is the evening rush hour for NOx at such a late time (~8:00-9:00 PM local time). I would expect the rush hour to be between 4:00 and 7:00 PM local time.
5) Fig. 4: why are some of the flight paths thicker?
6) Fig. 7: I would recommend the observations have a black outline as they are hard to see with the background model results.
-
RC2: 'Reply on RC1', Anonymous Referee #1, 03 Dec 2021
Forgot the references:
Choi et al. Assessment of NO2 observations during DISCOVER-AQ and KORUS-AQ field campaigns. https://doi.org/10.5194/amt-13-2523-2020. 2020.
Flynn et al. Relationship between column-density and surface mixing ratio: Statistical analysis of O3 and NO2 data from the July 2011 Maryland DISCOVER-AQ mission. AE. https://doi.org/10.1016/j.atmosenv.2014.04.041. 2014.
Flynn et al. Variability of O3 and NO2 profile shapes during DISCOVER-AQ: Implications for satellite observations and comparisons to model-simulated profiles. AE. https://doi.org/10.1016/j.atmosenv.2016.09.068. 2016.
Li et al. Comprehensive evaluations of diurnal NO2 measurements during DISCOVER-AQ 2011: effects of resolution-dependent representation of NOx emissions. ACP. https://doi.org/10.5194/acp-21-11133-2021. 2021.
Valin et al. Variations of OH radical in an urban plume inferred from NO2 column measurements. GRL. https://doi.org/10.1002/grl.50267. 2013.
- AC3: 'Reply on RC2', Ralf Tillmann, 23 Feb 2022
- AC1: 'Reply on RC1', Ralf Tillmann, 22 Feb 2022
-
RC2: 'Reply on RC1', Anonymous Referee #1, 03 Dec 2021
-
RC3: 'Comment on amt-2021-360', Anonymous Referee #2, 27 Dec 2021
Tillmann et al. provide an overview of the utilization of a new Zeppelin research platform equipped with instrumentation for air quality studies. They provide some examples of the unique sampling strategies that can be provided with such a platform (i.e. details of the vertical structure of the boundary layer) and the use of the platform to evaluate an emissions inventory.
Generally I think that what is presented is well done. Since the paper is submitted to AMT, I was expecting some more details on the evaluation of the data quality from the different instruments onboard. As far as I can tell, the measurements presented are only from the MIRO instrument. I think it would be appropriate to have a section discussing the data quality from the less expensive chemical sensors, and comment on their utility for the future. Was the intention of integrating them along with the MIRO to evaluate them, or was it to possibly rely on those only in the future for this or other platforms?
On the MIRO side, not all of the chemical measurements were discussed. I think it would be good to comment on the SO2 and NH3 data quality, since these are important for air quality studies and the use of a single instrument capable of providing all of those measurement would be really of wide interest. As the manuscript is though, we don’t know if those measurements were deemed to be of sufficient quality for air quality research.
I think that it may be appropriate for a revised version of the paper to be published in AMT, but think that first the sections that deal with the instrumentation should be expanded a bit to:
- Provide some comments on the observed data quality or issues from the MIRO, for example how much did the zeros drift?
- Expand the data discussion to comment at least on the SO2 and NH3 measurement, and
- Compare the measurements between MIRO and the sensors.
- AC2: 'Reply on RC3', Ralf Tillmann, 22 Feb 2022
Ralf Tillmannn et al.
Ralf Tillmannn et al.
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