the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 12 Jun 2023
Measurement Report: The Palau Atmospheric Observatory and its Ozonesonde Record - Continuous Monitoring of Tropospheric Composition and Dynamics in the Tropical West Pacific
Abstract. The Tropical West Pacific is recognized as an important region for stratosphere-troposphere exchange, but has been a measurement gap in the global ozone sounding network. The Palau Atmospheric Observatory (PAO) was established to study the atmospheric composition above the remote Tropical West Pacific with a comprehensive instrumental setup. Since 2016, two laboratory containers in Palau host an Fourier-transform infrared spectrometer, a lidar (micro lidar until 2016, cloud and aerosol lidar from 2018), a Pandora 2S photometer and laboratory space for weather balloon soundings with ozone-, water-vapor-, aerosol- and radiosondes. In this analysis, we focus on the continuous, fortnightly ozone sounding program with Electrochemical Concentration Cell (ECC) ozone sondes.
The aim of this study is to introduce the PAO and its research potential, present the first observation of the typical seasonal cycle of tropospheric ozone in the Tropical West Pacific based on a multiannual record of in situ observations, and investigate major drivers of variability and seasonal variation from 01/2016 until 12/2021 related to the large scale atmospheric circulation. We present the PAO ozone (O3) volume mixing ratios (VMR) and relative humidity (RH) time series complemented by other observations.
The site is exposed to year-round high convective activity reflected in dominating low O3 VMR and high RH. In 2016, the impact of the strong El Niño is evident as a particularly dry, ozone-rich episode. The main modulator of annual tropospheric O3 variability is identified as the movement of the Intertropical Convergence Zone (ITCZ), with lowest O3 VMR in the free troposphere during the ITCZ position north of Palau. An analysis of the relation of O3 and RH for the PAO and selected sites from the Southern Hemispheric ADditional OZonesondes (SHADOZ) network reveals three different regimes. Palau’s O3/RH distribution resembles the one in Fiji, Java and American Samoa, but is unique in its seasonality and its comparably narrow Gaussian distribution around low O3 VMR and the evenly distributed RH. A previously found bimodal distribution of O3 VMR and RH could not be seen in the Palau record.
Due to its unique remote location, Palau is an ideal atmospheric background site to detect changes in air dynamics imprinted on the chemical composition of the tropospheric column. The efforts to establish, run and maintain the PAO have succeeded to fill an observational gap in the remote Tropical West Pacific and give good prospects for ongoing operations. The ECC sonde record will be integrated into the SHADOZ database in the near future.
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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
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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-2023-1023', Anonymous Referee #1, 10 Jul 2023
Review Report
Measurement Report: The Palau Atmospheric Observatory and its Ozonesonde Record - Continuous Monitoring of Tropospheric Composition and Dynamics in the Tropical West Pacific
By Müller et al.
This paper provides a first overview of the ozonesonde and radiosonde data taken at the Palau Atmospheric Observatory (PAO) in the tropical western Pacific for six years from 2016 to 2021. After describing various ground-based observations at the PAO, the authors discuss variations of ozone, relative humidity (RH), and other meteorological parameters at interannual and annual time scales. They also compare PAO ozonesonde data from those taken at SHADOZ stations and from an aircraft campaign data.
This manuscript, as a Measurement Report, is a very good introduction to the PAO ozonesonde measurements, and is written basically very well. I think that it will be acceptable for publication in Atmospheric Chemistry and Physics after considering my comments below.
My major comments are regarding Section 3.2.2 Comparison with CONTRAST.
Is the definition of RH the same between Pan et al. (2014) and this paper? I assume that this paper simply uses the radiosonde readings which are RH over liquid water, while it is probably not clearly written in the paper by Pan et al. (2014) whether they also used this, or RH over ice for temperatures colder than e.g. -20 deg.C. For the comparison in this Section 3.2.2, the same definition of RH should be used.
Related to this, the choice of definition of RH in other subsections of Section 3 might be an issue (e.g. Figure 7). If the authors use the RH over liquid water, RH values tend to be lower at higher altitudes (and never get near 100 %RH above ~5 km in the tropics; see e.g. Fujiwara et al., 2003, their Figure 1), which may give biased results when analyzing data for the whole troposphere simultaneously.
Fujiwara, M., M. Shiotani, F. Hasebe, H. Vömel, S. J. Oltmans, P. W. Ruppert, T. Horinouchi, and T. Tsuda (2003), Performance of the Meteolabor "Snow White" chilled-mirror hygrometer in the tropical troposphere: Comparisons with the Vaisala RS80 A/H-Humicap sensors, Journal of Atmospheric and Oceanic Technology, 20, Issue 11, 1534-1542.
Another comment for Section 3.2.2 is as follows. As the CONTRAST campaign was conducted during January-February, the result for the analysis of PAO ozonesonde data in this season only would also be interesting. Do you obtain similar results when limiting the season? In addition, is there any dependence on the ENSO phase?
Below are minor comments and suggestions.
Line 2 and line 42 : The latitude and longitude information of PAO should be shown here.
Line 128: “The pressure dependent background current correction” should be explained here, by showing the equation. This is because it looks this is the only point where the authors do not follow the published, recent recommendations for ozonesonde data processing.
Line 174: Vömel et al. (2016) discuss an update on the uncertainties of CFH measurements.
Vömel, H., Naebert, T., Dirksen, R., and Sommer, M.: An update on the uncertainties of water vapor measurements using cryogenic frost point hygrometers, Atmos. Meas. Tech., 9, 3755–3768, doi:10.5194/amt-9-3755-2016, 2016.
Lines 180-: Section 2.3: Reference papers should be shown, at least for Bruker 120 M and SFIT4 code.
Lines 186-187: “-1” should be superscript.
Line 197: / should be ,
Line 208: Change the locations of (
Line 241: MEI: Are positive (negative) MEIs indicating El Nino (La Nina) events. Please explain this here.
Line 274 vs. line 284: Use either El Nino/La Nina events or warm/cold ENSO events consistently to avoid confusion for non-experts on the ENSO terminology.
Line 368: Is there any contribution from the dependence on the radiosonde model used? (Kuala Lumpur is the only station where GRAW radiosonde has been used?)
Line 567-568: Müller et al. (2023) has been cited several times in the manuscript, but currently it is “to be submitted”. While I am very much looking forward to that paper, I point this out here to the editor who might have concerns from the editorial viewpoint.
Citation: https://doi.org/10.5194/egusphere-2023-1023-RC1 -
RC2: 'Comment on egusphere-2023-1023', Anonymous Referee #2, 14 Jul 2023
Review of “Measurement Report: The Palau Atmospheric Observatory and its Ozonesonde Record - Continuous Monitoring of Tropospheric Composition and Dynamics in the Tropical West Pacific” by Müller et al.
Summary and General Comments:
This paper presents a detailed introduction to the Palau Atmospheric Observatory (PAO) with specific focus on the ~twice monthly ECC ozonesonde profiles that have been carried out since 2016. The paper is well written and provides excellent background information on PAO and its unique location, the ozonesonde data set, comparisons with nearby SHADOZ sites, the effects of large-scale climate oscillations, and examination of so-called “high ozone/low water vapor”, and vice-versa, features.
I was surprised and in principle do not agree with the pressure-dependent background for the ECC profiles here and as described in the Müller (2020) PhD thesis. As noted in the paper, this is certainly not the recommendation of the ASOPOS/ASOPOS 2.0 Panels. Nonetheless, the application of this correction avoids the near-zero ozone observations in the UT/LS in this region that previous work has shown to be false. For future studies of UT/LS low ozone amounts in the region, corrections for the slow reaction pathway as outlined in Vömel et al. (2020) and Smit et al. (2023; new reference, see below) and discarding of the pressure-dependent background should be examined. I would like to see more discussion on this data processing choice and the ECC slow time response as justification since it is a critical issue in the UT/LS above PAO. For example, what were typical background currents Ib0, 1, and 2 for this data set? Were background currents sufficiently low so that a pressure-dependent background current correction has little effect on the calculated profiles?
Smaller note: several times we are asked to consult a yet to be submitted Müller et al. (2023) paper. I suggest removing this reference for now, although by the time a final version of this paper is accepted, that may become available and it will be appropriate to add back in.
Recommendation:
I recommend this paper for publication after some additional discussion noted above, and very minor technical corrections as follows.
Specific and Line-by-Line Comments:
Line 61: Extra space after “/”
Line 164: I assume you have examined the pump temperatures for potential solution freezing/boiling effects as well, correct?
Line 193: Fix the quotations here
Line 212: analyses
Line 216: What type of radiosondes are launched there? If RS41 with its superior RH measurement, this would be an excellent data set for examining TTL RH.
Line 231: Thompson et al. (2021; https://doi.org/10.1029/2021JD034691) also used these distinguished characteristics to calculate regional ozone trends from SHADOZ data.
Figure 5 caption: “the a prominent layer” delete “the”
New paper to consider citing for discussion of the ECC “background” current and correction of the time response delay of the ozonesonde:
Smit, H. G. J., Poyraz, D., Van Malderen, R., Thompson, A. M., Tarasick, D. W., Stauffer, R. M., Johnson, B. J., and Kollonige, D. E.: New Insights From The Jülich Ozone-Sonde Intercomparison Experiments: Calibration Functions Traceable To One Ozone Reference Instrument, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-1466, 2023.
Citation: https://doi.org/10.5194/egusphere-2023-1023-RC2 - AC1: 'AC- Comment on egusphere-2023-1023', Katrin Müller, 25 Oct 2023
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-1023', Anonymous Referee #1, 10 Jul 2023
Review Report
Measurement Report: The Palau Atmospheric Observatory and its Ozonesonde Record - Continuous Monitoring of Tropospheric Composition and Dynamics in the Tropical West Pacific
By Müller et al.
This paper provides a first overview of the ozonesonde and radiosonde data taken at the Palau Atmospheric Observatory (PAO) in the tropical western Pacific for six years from 2016 to 2021. After describing various ground-based observations at the PAO, the authors discuss variations of ozone, relative humidity (RH), and other meteorological parameters at interannual and annual time scales. They also compare PAO ozonesonde data from those taken at SHADOZ stations and from an aircraft campaign data.
This manuscript, as a Measurement Report, is a very good introduction to the PAO ozonesonde measurements, and is written basically very well. I think that it will be acceptable for publication in Atmospheric Chemistry and Physics after considering my comments below.
My major comments are regarding Section 3.2.2 Comparison with CONTRAST.
Is the definition of RH the same between Pan et al. (2014) and this paper? I assume that this paper simply uses the radiosonde readings which are RH over liquid water, while it is probably not clearly written in the paper by Pan et al. (2014) whether they also used this, or RH over ice for temperatures colder than e.g. -20 deg.C. For the comparison in this Section 3.2.2, the same definition of RH should be used.
Related to this, the choice of definition of RH in other subsections of Section 3 might be an issue (e.g. Figure 7). If the authors use the RH over liquid water, RH values tend to be lower at higher altitudes (and never get near 100 %RH above ~5 km in the tropics; see e.g. Fujiwara et al., 2003, their Figure 1), which may give biased results when analyzing data for the whole troposphere simultaneously.
Fujiwara, M., M. Shiotani, F. Hasebe, H. Vömel, S. J. Oltmans, P. W. Ruppert, T. Horinouchi, and T. Tsuda (2003), Performance of the Meteolabor "Snow White" chilled-mirror hygrometer in the tropical troposphere: Comparisons with the Vaisala RS80 A/H-Humicap sensors, Journal of Atmospheric and Oceanic Technology, 20, Issue 11, 1534-1542.
Another comment for Section 3.2.2 is as follows. As the CONTRAST campaign was conducted during January-February, the result for the analysis of PAO ozonesonde data in this season only would also be interesting. Do you obtain similar results when limiting the season? In addition, is there any dependence on the ENSO phase?
Below are minor comments and suggestions.
Line 2 and line 42 : The latitude and longitude information of PAO should be shown here.
Line 128: “The pressure dependent background current correction” should be explained here, by showing the equation. This is because it looks this is the only point where the authors do not follow the published, recent recommendations for ozonesonde data processing.
Line 174: Vömel et al. (2016) discuss an update on the uncertainties of CFH measurements.
Vömel, H., Naebert, T., Dirksen, R., and Sommer, M.: An update on the uncertainties of water vapor measurements using cryogenic frost point hygrometers, Atmos. Meas. Tech., 9, 3755–3768, doi:10.5194/amt-9-3755-2016, 2016.
Lines 180-: Section 2.3: Reference papers should be shown, at least for Bruker 120 M and SFIT4 code.
Lines 186-187: “-1” should be superscript.
Line 197: / should be ,
Line 208: Change the locations of (
Line 241: MEI: Are positive (negative) MEIs indicating El Nino (La Nina) events. Please explain this here.
Line 274 vs. line 284: Use either El Nino/La Nina events or warm/cold ENSO events consistently to avoid confusion for non-experts on the ENSO terminology.
Line 368: Is there any contribution from the dependence on the radiosonde model used? (Kuala Lumpur is the only station where GRAW radiosonde has been used?)
Line 567-568: Müller et al. (2023) has been cited several times in the manuscript, but currently it is “to be submitted”. While I am very much looking forward to that paper, I point this out here to the editor who might have concerns from the editorial viewpoint.
Citation: https://doi.org/10.5194/egusphere-2023-1023-RC1 -
RC2: 'Comment on egusphere-2023-1023', Anonymous Referee #2, 14 Jul 2023
Review of “Measurement Report: The Palau Atmospheric Observatory and its Ozonesonde Record - Continuous Monitoring of Tropospheric Composition and Dynamics in the Tropical West Pacific” by Müller et al.
Summary and General Comments:
This paper presents a detailed introduction to the Palau Atmospheric Observatory (PAO) with specific focus on the ~twice monthly ECC ozonesonde profiles that have been carried out since 2016. The paper is well written and provides excellent background information on PAO and its unique location, the ozonesonde data set, comparisons with nearby SHADOZ sites, the effects of large-scale climate oscillations, and examination of so-called “high ozone/low water vapor”, and vice-versa, features.
I was surprised and in principle do not agree with the pressure-dependent background for the ECC profiles here and as described in the Müller (2020) PhD thesis. As noted in the paper, this is certainly not the recommendation of the ASOPOS/ASOPOS 2.0 Panels. Nonetheless, the application of this correction avoids the near-zero ozone observations in the UT/LS in this region that previous work has shown to be false. For future studies of UT/LS low ozone amounts in the region, corrections for the slow reaction pathway as outlined in Vömel et al. (2020) and Smit et al. (2023; new reference, see below) and discarding of the pressure-dependent background should be examined. I would like to see more discussion on this data processing choice and the ECC slow time response as justification since it is a critical issue in the UT/LS above PAO. For example, what were typical background currents Ib0, 1, and 2 for this data set? Were background currents sufficiently low so that a pressure-dependent background current correction has little effect on the calculated profiles?
Smaller note: several times we are asked to consult a yet to be submitted Müller et al. (2023) paper. I suggest removing this reference for now, although by the time a final version of this paper is accepted, that may become available and it will be appropriate to add back in.
Recommendation:
I recommend this paper for publication after some additional discussion noted above, and very minor technical corrections as follows.
Specific and Line-by-Line Comments:
Line 61: Extra space after “/”
Line 164: I assume you have examined the pump temperatures for potential solution freezing/boiling effects as well, correct?
Line 193: Fix the quotations here
Line 212: analyses
Line 216: What type of radiosondes are launched there? If RS41 with its superior RH measurement, this would be an excellent data set for examining TTL RH.
Line 231: Thompson et al. (2021; https://doi.org/10.1029/2021JD034691) also used these distinguished characteristics to calculate regional ozone trends from SHADOZ data.
Figure 5 caption: “the a prominent layer” delete “the”
New paper to consider citing for discussion of the ECC “background” current and correction of the time response delay of the ozonesonde:
Smit, H. G. J., Poyraz, D., Van Malderen, R., Thompson, A. M., Tarasick, D. W., Stauffer, R. M., Johnson, B. J., and Kollonige, D. E.: New Insights From The Jülich Ozone-Sonde Intercomparison Experiments: Calibration Functions Traceable To One Ozone Reference Instrument, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-1466, 2023.
Citation: https://doi.org/10.5194/egusphere-2023-1023-RC2 - AC1: 'AC- Comment on egusphere-2023-1023', Katrin Müller, 25 Oct 2023
Peer review completion
Journal article(s) based on this preprint
Data sets
Ozone sonde and radio sonde data record Palau Atmospheric Observatory 2016-2021 (V1.0) Katrin Müller, Jürgen Graeser, Sharon Patris, Ingo Beninga, Wilfried Ruhe, Gerda Ucharm, and Jordis Tradowsky https://doi.org/10.5281/zenodo.6920648
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Cited
Jordis S. Tradowsky
Peter von der Gathen
Christoph Ritter
Sharon Patris
Justus Notholt
Markus Rex
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(18055 KB) - Metadata XML