Shift in cold-point tropopause trends derived from radiosonde, satellite, and reanalysis data

Zolghadrshojaee, Mona; Tegtmeier, Susann; Davis, Sean M.; Pilch Kedzierski, Robin; Haimberger, Leopold

doi:https://doi.org/10.5194/egusphere-2025-82

Preprints

https://doi.org/10.5194/egusphere-2025-82

Preprints

11 Feb 2025

| 11 Feb 2025

Shift in cold-point tropopause trends derived from radiosonde, satellite, and reanalysis data

Mona Zolghadrshojaee, Susann Tegtmeier, Sean M. Davis, Robin Pilch Kedzierski, and Leopold Haimberger

Abstract. The tropical tropopause layer (TTL) is the transition region between the well-mixed convective troposphere and the radiatively controlled stratosphere and plays a crucial role for air mass transport between these layers. In this paper, we present updated trends of TTL and lower stratospheric temperature from radiosonde and Global Navigation Satellite System – Radio Occultation (GNSS-RO) data and evaluate temperature trends in the reanalysis data sets ERA5, JRA-3Q, and MERRA-2. Given its importance in determining the concentration of water vapor entering the stratosphere, we focused in particular on temperature trends at the cold point tropopause, which we determined from radiosonde observations by removing time-varying bias effects from trends based on unadjusted data.

From 1980 to 2023, cold point tropopause cooling is shown in radiosondes, overestimated by JRA-3Q and underestimated by MERRA-2 and ERA5. Splitting into two periods reveals a shift in TTL temperature trends: cooling (1980–2001) to warming (2002–2023) across all datasets, highlighting post-2002 changes in tropical tropopause dynamics. Tropical upwelling estimates from the three reanalyses show opposite trends for 1980–2001 compared to 2002–2023 consistent with the cold point and lower stratosphere temperature trends. While the vertical residual circulation increased before 2000 consistent with cold point cooling, the circulation trends turned to zero (MERRA-2, JRA-3Q) or became positive (ERA5) after 2000 consistent with cold point warming. Between 2002–2023, GNSS-RO and reanalysis show significant warming at the cold point and lower stratosphere, aligning with observed patterns and seasonality. Warming trends anticorrelate with tropospheric cooling, strongest where upper troposphere cooling appears.

Received: 08 Jan 2025 – Discussion started: 11 Feb 2025

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Journal article(s) based on this preprint

07 Oct 2025

Shift in cold-point tropopause trends derived from radiosonde, satellite and reanalysis data

Mona Zolghadrshojaee, Susann Tegtmeier, Sean M. Davis, Robin Pilch Kedzierski, and Leopold Haimberger

Atmos. Chem. Phys., 25, 12213–12232, https://doi.org/10.5194/acp-25-12213-2025,https://doi.org/10.5194/acp-25-12213-2025, 2025

Short summary

Mona Zolghadrshojaee, Susann Tegtmeier, Sean M. Davis, Robin Pilch Kedzierski, and Leopold Haimberger

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-82', Anonymous Referee #1, 31 Mar 2025

The authors employed radiosonde, GNSS-RO, and reanalyses to update the long-term variations of temperature in the tropical upper troposphere and lower stratosphere, with a particular focus on cold point temperature. As the authors mention in the introduction, there are already many previous studies that use various data sources, including reanalysis, radiosonde, and GNSS-RO. However, a detailed comparison with previous studies is necessary to highlight the novelty of the present study. Furthermore, while the authors attempted to conduct their research using multiple datasets with high vertical resolution, they did not reveal novel or more refined features, nor did they propose new mechanisms for existing trends. Despite the study's objective to quantify trends in both space and time, it does not address the scientific questions that exist in this area. The current state of the manuscript lacks sufficient novelty for publication in the Atmospheric Chemistry and Physics.
Major Comments
1 As suggested by Highwood and Hoskins (1998), the cold-point is only a reliable tropopause definition when the lower stratosphere is not close to being isothermal, i.e., within the deep tropics. Beyond the deep tropics, the validity of the physical significance of cold point identified in the research region [30S-30N] must be assured.
2 What are the differences between the trend term derived from multivariate linear regression and that derived from conventional linear regression? Furthermore, it is crucial to ascertain the magnitude of the contributions of the additional terms (QBO, ENSO, SAOD) in the multivariate linear regression.
3 GNSS-RO measurements exhibit pronounced irregularities in the tropics compared to middle latitudes. The authors use a relatively large grid (30° longitude × 10° latitude) to ensure sufficient data sampling. However, early single GNSS-RO missions were capable of providing only about 100 profiles per day globally. For instance, the CHAMP (2001-2007) and GRACE (2006-2007) satellites each provided approximately 130 daily profiles. By contrast, the COSMIC constellation, operational since late 2007, provides about 2,500 measurements daily. This substantial disparity highlights significant sampling inhomogeneity. Given the use of multiple missions to construct long-term observations, how do the authors account for sampling biases arising from mission prioritization?
4 What implications might be drawn from the observation of significant upper troposphere warming in conjunction with insignificant temperature trends in both the cold point and lower stratosphere, as illustrated in Figure 6? Furthermore, it is important to consider the implications of these phenomena in relation to radiative or radiative-dynamical balances.
5 A discussion is also required regarding the discrepancy between the trends derived from different datasets.
6 An important question concerns the apparent shift in long-term trends around the year 2000. While the authors have proposed several potential mechanisms for this shift, a more thorough discussion is needed to fully explore these possibilities.
7 Given the apparent decoupling of upwelling trends and warming trends, it is necessary to explore alternative mechanisms that could explain the observed changes. The authors propose a correlation between the warming of the cold point and the weakening of BDC (Ln 305). This relationship should be quantitatively assessed through a rigorous analysis of reanalysis data.
Regarding the zonal-mean dynamical variables from Martineau et al. (2018) (covering 1958-2016), clarification is needed as to whether the vertical residual velocities were: (1) calculated following Martineau's methodology, or (2) obtained directly from the archived data. The relevant description in Lines 184-186 should be revised to clarify this point, or alternatively, the Data Availability statement should be updated accordingly.

Minor comments
Section 2.1 requires rewording. The methodology suggests that the cold point is determined for each radiosonde profile prior to the gridding procedure.
Ln 152-154 Please rephrase this sentence
Ln 158 balloon reading?
Ln 175 It is necessary to establish the reasons for the observation of a comparatively wider range of cold points in reanalyses as compared with radiosonde observations.
Ln 194 In fact, the short-term variations are left in the error term
It appears that reference to Table 1 has not been made in Ln 326-332.

Citation: https://doi.org/10.5194/egusphere-2025-82-RC1
- AC1: 'Reply on RC1', Mona Zolghadrshojaee, 15 Jul 2025
  
  Detailed responses are attached in the PDF file below.
  
  Citation: https://doi.org/10.5194/egusphere-2025-82-AC1
RC2:
'Comment on egusphere-2025-82', Anonymous Referee #2, 02 Apr 2025

In this study temperature trends are derived from radiosonde, satellite and reanalysis data with special focus on the cold point tropopause. Thereby, the period for which the trend is estimated is extended compared to previous study and covers the time period from 1980-2023, thus more than 40 years. Although this study does not present any significant new results it merits in my opinion publication. The extension of the data considered and the according update in trend estimates justifies a publication since if I understand the summary of previous studies correctly the time periods previously considered where much shorter. Thus, analyzing here about 40 years of data is quite valuable for deriving reliable trend estimates. However, the writing of the manuscript should be improved to better point out what the highlights and major results of this study are.
Specific comments:
Abstract: The abstract needs to be improved. For example, the second paragraph is providing too many details on the results without making clear what the main result is and what the implications of this study are.
P3, L79: You consider here a time period of 40 years! This could be more clearly be pointed out. Especially since it seems that earlier studies considered significantly shorter time periods which were considering max ~ 20 years.
P3, L84: The authors published last year a paper on this topic. It would be worth to also clearly point out what the differences between your previous study and this study are.
P3, L86: Section 2, especially the sections about the radiosonde data could be improved. I had trouble to understand what the differences between the adjusted and unadjusted data is. I had the feeling that you here also got lost a bit in details. I would suggest to put 2.1 and 2.2 in one subsection (thus 2.1 and called “Radiosonde data”) and then start with an introductory sentence and then have two subsubsection headers (with or without section numbering) on the adjusted and unadjusted radiosonde data.
P4, L116ff: Does this paragraph really belong to this subsection? I had rather the feeling this is part of the result section.
P4, L120: Has the abbreviation “QBO” been introduced?
P6, 158-170: Is this information really necessary. I have the feeling also here too many details are provided which are not important for understanding this study.
P6, L171-181: I think it would be much more helpful to list these differences in a table.
P5-7: The reanalysis data section is too long and I had the feeling too many results are presented here that are not necessary for understanding your study.
P8, L219-220: If in both cases the same pressure levels have been used the sentence could be formulated much shorter and clearer.
P8, L234-236: The latter part in the sentence “The good agreement of the four trend estimates highlights the consistency of the CPT temperature trends derived from adjusted data sets, which are only half of the cooling trend suggested by unadjusted data.” not clear. Please rephrase.
P9, L244: Add “e.g.” before the reference “Randel et al.”.
P16, L374: Add here one or two sentences summarizing what has been done in this study.
P17 , L387-389: This is an important result and should be mentioned at several places in the manuscript and not solely in the middle of the discussion.
All figures: Put the units in the title in parentheses instead of brackets.
Technical corrections:
P6, L173: space between number and unit missing.
P8, L224: space between number and unit missing.
P11, L283: in the Appendix A section -> in Appendix A
P19, L445: ozon e -> ozone
P25, Appendix: Start with the Appendix on a new page.

Citation: https://doi.org/10.5194/egusphere-2025-82-RC2
- AC2: 'Reply on RC2', Mona Zolghadrshojaee, 15 Jul 2025
  
  Author response to referee comments on
  
  “Shift in cold-point tropopause trends derived from radiosonde, satellite, and reanalysis data
  
  by Zolghadrshojaee et al.
  
  Anonymous Referee #2
  
  In this study temperature trends are derived from radiosonde, satellite and reanalysis data with special focus on the cold point tropopause. Thereby, the period for which the trend is estimated is extended compared to previous study and covers the time period from 1980-2023, thus more than 40 years. Although this study does not present any significant new results it merits in my opinion publication. The extension of the data considered and the according update in trend estimates justifies a publication since if I understand the summary of previous studies correctly the time periods previously considered where much shorter. Thus, analyzing here about 40 years of data is quite valuable for deriving reliable trend estimates. However, the writing of the manuscript should be improved to better point out what the highlights and major results of this study are.
  We thank the referee for their valuable comments. We have changed the manuscript according to the comments listed below. Most importantly, we have rewritten the abstract, shortened some of the data sections and streamlined the discussion of the different potential mechanisms and implications of the shift in temperature trends in the TTL. We have also added information on the explained temperature variability and a sensitivity study analyzing sampling density and choice of regression model. As a result of these and other changes, the manuscript has clearly improved now better highlighting the major results of the study. Comments are reproduced below, followed by our responses in blue font.
  
  Specific comments:
  Abstract: The abstract needs to be improved. For example, the second paragraph is providing too many details on the results without making clear what the main result is and what the implications of this study are.
  Thanks for pointing this out. We have completely rewritten the second paragraph of the abstract, which is now more focused on the main results as well as potential mechanisms and implications.
  P3, L79: You consider here a time period of 40 years! This could be more clearly be pointed out. Especially since it seems that earlier studies considered significantly shorter time periods which were considering max ~ 20 years.
  We have added this fact here and in other places.
  P3, L84: The authors published last year a paper on this topic. It would be worth to also clearly point out what the differences between your previous study and this study are.
  We have added one sentence here highlighting the differences between the two studies.
  P3, L86: Section 2, especially the sections about the radiosonde data could be improved. I had trouble to understand what the differences between the adjusted and unadjusted data is. I had the feeling that you here also got lost a bit in the details. I would suggest to put 2.1 and 2.2 in one subsection (thus 2.1 and called “Radiosonde data”) and then start with an introductory sentence and then have two subsubsection headers (with or without section numbering) on the adjusted and unadjusted radiosonde data.
  Thanks for the suggestion, we have restructured sections 2.1 and 2.2 accordingly and have added short summary of the differences between the two data types.
  P4, L116ff: Does this paragraph really belong to this subsection? I had rather the feeling this is part of the result section.
  Given that the very good agreement of the residuals from adjusted and unadjusted data at the fixed pressure levels is an important prerequisite for our methodology, we prefer to show this figure before the method section.
  P4, L120: Has the abbreviation “QBO” been introduced?
  The name has been added.
  P6, 158-170: Is this information really necessary. I have the feeling also here too many details are provided which are not important for understanding this study.
  We have considerably shortened this paragraph.
  P6, L171-181: I think it would be much more helpful to list these differences in a table.
  We have considerably shortened and restructured this section, but decided to not introduce a table given that there are only 3 quantities that would be included in such as table.
  P5-7: The reanalysis data section is too long and I had the feeling too many results are presented here that are not necessary for understanding your study.
  We have considerably shortened this section by removing some details.
  P8, L219-220: If in both cases the same pressure levels have been used the sentence could be formulated much shorter and clearer.
  I can’t really see how this sentence could be formulated much shorter.
  P8, L234-236: The latter part in the sentence “The good agreement of the four trend estimates highlights the consistency of the CPT temperature trends derived from adjusted data sets, which are only half of the cooling trend suggested by unadjusted data.” not clear. Please rephrase.
  We have rephrased the sentence as ‘The good agreement of the four trend estimates based on adjusted data highlights the consistency of our method when applied to different pressure levels or data sets. These adjusted trends are only half of the cooling trend suggested by unadjusted data, reaffirming that inhomogeneities in the latter can impact the trend estimates.‘
  P9, L244: Add “e.g.” before the reference “Randel et al.”.
  Done.
  P16, L374: Add here one or two sentences summarizing what has been done in this study.
  We have added one sentence summarizing what has been done.
  P17 , L387-389: This is an important result and should be mentioned at several places in the manuscript and not solely in the middle of the discussion.
  We have now highlighted this shift in cold-point trends in other parts of the manuscript such as the abstract and overall conclusion section. We also extended the conclusion section with a discussion of the different mechanisms that can impact the shift in temperature trends in the TTL and possible implications
  All figures: Put the units in the title in parentheses instead of brackets.
  Done.
  Technical corrections:
  P6, L173: space between number and unit missing.
  P8, L224: space between number and unit missing.
  P11, L283: in the Appendix A section -> in Appendix A
  P19, L445: ozon e -> ozone
  P25, Appendix: Start with the Appendix on a new page.
  All changes have been made.
  
  Citation: https://doi.org/10.5194/egusphere-2025-82-AC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-82', Anonymous Referee #1, 31 Mar 2025

The authors employed radiosonde, GNSS-RO, and reanalyses to update the long-term variations of temperature in the tropical upper troposphere and lower stratosphere, with a particular focus on cold point temperature. As the authors mention in the introduction, there are already many previous studies that use various data sources, including reanalysis, radiosonde, and GNSS-RO. However, a detailed comparison with previous studies is necessary to highlight the novelty of the present study. Furthermore, while the authors attempted to conduct their research using multiple datasets with high vertical resolution, they did not reveal novel or more refined features, nor did they propose new mechanisms for existing trends. Despite the study's objective to quantify trends in both space and time, it does not address the scientific questions that exist in this area. The current state of the manuscript lacks sufficient novelty for publication in the Atmospheric Chemistry and Physics.
Major Comments
1 As suggested by Highwood and Hoskins (1998), the cold-point is only a reliable tropopause definition when the lower stratosphere is not close to being isothermal, i.e., within the deep tropics. Beyond the deep tropics, the validity of the physical significance of cold point identified in the research region [30S-30N] must be assured.
2 What are the differences between the trend term derived from multivariate linear regression and that derived from conventional linear regression? Furthermore, it is crucial to ascertain the magnitude of the contributions of the additional terms (QBO, ENSO, SAOD) in the multivariate linear regression.
3 GNSS-RO measurements exhibit pronounced irregularities in the tropics compared to middle latitudes. The authors use a relatively large grid (30° longitude × 10° latitude) to ensure sufficient data sampling. However, early single GNSS-RO missions were capable of providing only about 100 profiles per day globally. For instance, the CHAMP (2001-2007) and GRACE (2006-2007) satellites each provided approximately 130 daily profiles. By contrast, the COSMIC constellation, operational since late 2007, provides about 2,500 measurements daily. This substantial disparity highlights significant sampling inhomogeneity. Given the use of multiple missions to construct long-term observations, how do the authors account for sampling biases arising from mission prioritization?
4 What implications might be drawn from the observation of significant upper troposphere warming in conjunction with insignificant temperature trends in both the cold point and lower stratosphere, as illustrated in Figure 6? Furthermore, it is important to consider the implications of these phenomena in relation to radiative or radiative-dynamical balances.
5 A discussion is also required regarding the discrepancy between the trends derived from different datasets.
6 An important question concerns the apparent shift in long-term trends around the year 2000. While the authors have proposed several potential mechanisms for this shift, a more thorough discussion is needed to fully explore these possibilities.
7 Given the apparent decoupling of upwelling trends and warming trends, it is necessary to explore alternative mechanisms that could explain the observed changes. The authors propose a correlation between the warming of the cold point and the weakening of BDC (Ln 305). This relationship should be quantitatively assessed through a rigorous analysis of reanalysis data.
Regarding the zonal-mean dynamical variables from Martineau et al. (2018) (covering 1958-2016), clarification is needed as to whether the vertical residual velocities were: (1) calculated following Martineau's methodology, or (2) obtained directly from the archived data. The relevant description in Lines 184-186 should be revised to clarify this point, or alternatively, the Data Availability statement should be updated accordingly.

Minor comments
Section 2.1 requires rewording. The methodology suggests that the cold point is determined for each radiosonde profile prior to the gridding procedure.
Ln 152-154 Please rephrase this sentence
Ln 158 balloon reading?
Ln 175 It is necessary to establish the reasons for the observation of a comparatively wider range of cold points in reanalyses as compared with radiosonde observations.
Ln 194 In fact, the short-term variations are left in the error term
It appears that reference to Table 1 has not been made in Ln 326-332.

Citation: https://doi.org/10.5194/egusphere-2025-82-RC1
- AC1: 'Reply on RC1', Mona Zolghadrshojaee, 15 Jul 2025
  
  Detailed responses are attached in the PDF file below.
  
  Citation: https://doi.org/10.5194/egusphere-2025-82-AC1
RC2:
'Comment on egusphere-2025-82', Anonymous Referee #2, 02 Apr 2025

In this study temperature trends are derived from radiosonde, satellite and reanalysis data with special focus on the cold point tropopause. Thereby, the period for which the trend is estimated is extended compared to previous study and covers the time period from 1980-2023, thus more than 40 years. Although this study does not present any significant new results it merits in my opinion publication. The extension of the data considered and the according update in trend estimates justifies a publication since if I understand the summary of previous studies correctly the time periods previously considered where much shorter. Thus, analyzing here about 40 years of data is quite valuable for deriving reliable trend estimates. However, the writing of the manuscript should be improved to better point out what the highlights and major results of this study are.
Specific comments:
Abstract: The abstract needs to be improved. For example, the second paragraph is providing too many details on the results without making clear what the main result is and what the implications of this study are.
P3, L79: You consider here a time period of 40 years! This could be more clearly be pointed out. Especially since it seems that earlier studies considered significantly shorter time periods which were considering max ~ 20 years.
P3, L84: The authors published last year a paper on this topic. It would be worth to also clearly point out what the differences between your previous study and this study are.
P3, L86: Section 2, especially the sections about the radiosonde data could be improved. I had trouble to understand what the differences between the adjusted and unadjusted data is. I had the feeling that you here also got lost a bit in details. I would suggest to put 2.1 and 2.2 in one subsection (thus 2.1 and called “Radiosonde data”) and then start with an introductory sentence and then have two subsubsection headers (with or without section numbering) on the adjusted and unadjusted radiosonde data.
P4, L116ff: Does this paragraph really belong to this subsection? I had rather the feeling this is part of the result section.
P4, L120: Has the abbreviation “QBO” been introduced?
P6, 158-170: Is this information really necessary. I have the feeling also here too many details are provided which are not important for understanding this study.
P6, L171-181: I think it would be much more helpful to list these differences in a table.
P5-7: The reanalysis data section is too long and I had the feeling too many results are presented here that are not necessary for understanding your study.
P8, L219-220: If in both cases the same pressure levels have been used the sentence could be formulated much shorter and clearer.
P8, L234-236: The latter part in the sentence “The good agreement of the four trend estimates highlights the consistency of the CPT temperature trends derived from adjusted data sets, which are only half of the cooling trend suggested by unadjusted data.” not clear. Please rephrase.
P9, L244: Add “e.g.” before the reference “Randel et al.”.
P16, L374: Add here one or two sentences summarizing what has been done in this study.
P17 , L387-389: This is an important result and should be mentioned at several places in the manuscript and not solely in the middle of the discussion.
All figures: Put the units in the title in parentheses instead of brackets.
Technical corrections:
P6, L173: space between number and unit missing.
P8, L224: space between number and unit missing.
P11, L283: in the Appendix A section -> in Appendix A
P19, L445: ozon e -> ozone
P25, Appendix: Start with the Appendix on a new page.

Citation: https://doi.org/10.5194/egusphere-2025-82-RC2
- AC2: 'Reply on RC2', Mona Zolghadrshojaee, 15 Jul 2025
  
  Author response to referee comments on
  
  “Shift in cold-point tropopause trends derived from radiosonde, satellite, and reanalysis data
  
  by Zolghadrshojaee et al.
  
  Anonymous Referee #2
  
  In this study temperature trends are derived from radiosonde, satellite and reanalysis data with special focus on the cold point tropopause. Thereby, the period for which the trend is estimated is extended compared to previous study and covers the time period from 1980-2023, thus more than 40 years. Although this study does not present any significant new results it merits in my opinion publication. The extension of the data considered and the according update in trend estimates justifies a publication since if I understand the summary of previous studies correctly the time periods previously considered where much shorter. Thus, analyzing here about 40 years of data is quite valuable for deriving reliable trend estimates. However, the writing of the manuscript should be improved to better point out what the highlights and major results of this study are.
  We thank the referee for their valuable comments. We have changed the manuscript according to the comments listed below. Most importantly, we have rewritten the abstract, shortened some of the data sections and streamlined the discussion of the different potential mechanisms and implications of the shift in temperature trends in the TTL. We have also added information on the explained temperature variability and a sensitivity study analyzing sampling density and choice of regression model. As a result of these and other changes, the manuscript has clearly improved now better highlighting the major results of the study. Comments are reproduced below, followed by our responses in blue font.
  
  Specific comments:
  Abstract: The abstract needs to be improved. For example, the second paragraph is providing too many details on the results without making clear what the main result is and what the implications of this study are.
  Thanks for pointing this out. We have completely rewritten the second paragraph of the abstract, which is now more focused on the main results as well as potential mechanisms and implications.
  P3, L79: You consider here a time period of 40 years! This could be more clearly be pointed out. Especially since it seems that earlier studies considered significantly shorter time periods which were considering max ~ 20 years.
  We have added this fact here and in other places.
  P3, L84: The authors published last year a paper on this topic. It would be worth to also clearly point out what the differences between your previous study and this study are.
  We have added one sentence here highlighting the differences between the two studies.
  P3, L86: Section 2, especially the sections about the radiosonde data could be improved. I had trouble to understand what the differences between the adjusted and unadjusted data is. I had the feeling that you here also got lost a bit in the details. I would suggest to put 2.1 and 2.2 in one subsection (thus 2.1 and called “Radiosonde data”) and then start with an introductory sentence and then have two subsubsection headers (with or without section numbering) on the adjusted and unadjusted radiosonde data.
  Thanks for the suggestion, we have restructured sections 2.1 and 2.2 accordingly and have added short summary of the differences between the two data types.
  P4, L116ff: Does this paragraph really belong to this subsection? I had rather the feeling this is part of the result section.
  Given that the very good agreement of the residuals from adjusted and unadjusted data at the fixed pressure levels is an important prerequisite for our methodology, we prefer to show this figure before the method section.
  P4, L120: Has the abbreviation “QBO” been introduced?
  The name has been added.
  P6, 158-170: Is this information really necessary. I have the feeling also here too many details are provided which are not important for understanding this study.
  We have considerably shortened this paragraph.
  P6, L171-181: I think it would be much more helpful to list these differences in a table.
  We have considerably shortened and restructured this section, but decided to not introduce a table given that there are only 3 quantities that would be included in such as table.
  P5-7: The reanalysis data section is too long and I had the feeling too many results are presented here that are not necessary for understanding your study.
  We have considerably shortened this section by removing some details.
  P8, L219-220: If in both cases the same pressure levels have been used the sentence could be formulated much shorter and clearer.
  I can’t really see how this sentence could be formulated much shorter.
  P8, L234-236: The latter part in the sentence “The good agreement of the four trend estimates highlights the consistency of the CPT temperature trends derived from adjusted data sets, which are only half of the cooling trend suggested by unadjusted data.” not clear. Please rephrase.
  We have rephrased the sentence as ‘The good agreement of the four trend estimates based on adjusted data highlights the consistency of our method when applied to different pressure levels or data sets. These adjusted trends are only half of the cooling trend suggested by unadjusted data, reaffirming that inhomogeneities in the latter can impact the trend estimates.‘
  P9, L244: Add “e.g.” before the reference “Randel et al.”.
  Done.
  P16, L374: Add here one or two sentences summarizing what has been done in this study.
  We have added one sentence summarizing what has been done.
  P17 , L387-389: This is an important result and should be mentioned at several places in the manuscript and not solely in the middle of the discussion.
  We have now highlighted this shift in cold-point trends in other parts of the manuscript such as the abstract and overall conclusion section. We also extended the conclusion section with a discussion of the different mechanisms that can impact the shift in temperature trends in the TTL and possible implications
  All figures: Put the units in the title in parentheses instead of brackets.
  Done.
  Technical corrections:
  P6, L173: space between number and unit missing.
  P8, L224: space between number and unit missing.
  P11, L283: in the Appendix A section -> in Appendix A
  P19, L445: ozon e -> ozone
  P25, Appendix: Start with the Appendix on a new page.
  All changes have been made.
  
  Citation: https://doi.org/10.5194/egusphere-2025-82-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Mona Zolghadrshojaee on behalf of the Authors (15 Jul 2025) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (16 Jul 2025) by Farahnaz Khosrawi

ED: Publish subject to minor revisions (review by editor) (23 Jul 2025) by Farahnaz Khosrawi

Dear authors,

thanks for submitting the revised version of your manuscript. I am satisfied with your answers to the referee comments and the corresponding revision of your manuscript. However, I have several (rather technical) comments and corrections that should be considered before publication.

Specific comments:
P1, L10ff: The abstract is too long and needs to be shortened (see the new ACP author guidelines: https://www.atmospheric-chemistry-and-physics.net/policies/guidelines_for_authors.html, maximum allowed length is 250 words).
P2, L59-60: Please rephrase the sentence so that it becomes clear that Aura is the satellite and MLS the instrument onboard of it. A suggestion would be “…as detected by the Microwave Limb Sounder (MLS) onboard the NASA’s Aura satellite.”
P3, L81: I would suggest to rephrase the sentence as follows: “In our study, we aimed on updating existing studies of…….”.
P3, L82: I would suggest to write instead of “Our analysis will focus….” rather “Our analysis focuses on……”
P3, L87ff: “Section” should be abbreviated as “Sect.” unless it appears at the begin of the sentence (please correct this throughout the manuscript).
P4, L98: Add a reference for this statement?
P4, L107: Time is usually abbreviated with a small “t”, thus I would suggest to write “t00” or “t0” and “t12”.
P4, L115: The dataset? You mean the IGRA dataset. I would suggest to clearly state this.
P5, Figure 1 caption and all following figure captions: Only the text “Figure” with the respective number is written with bold face. The rest of the caption should have the same font as the text.
P6, L150-151: Abbreviations of the instrument names should be introduced and “Metop” should be written consistently as “Metop” or “METOP” (I think the correct writing is “Metop”).
P6, L162: Abbreviation “ECMWF” should be introduced.
P6, L167: This was rather an “update” of the current data set than a “new” data set.
P6, L173-175: Also here the instruments abbreviations should be introduced.
P7, L198, Sect. 3.1 title: error bars -> errors
P7, L210: Add here the also the abbreviation of this data set in parenthesis -> (GloSSAC)
P8, L215: Write here in the section header Nearby Level also with quotation marks -> ‘Nearby Level’
P10, L274: I would suggest to move “with differences of less than 10%” behind “very similar” and using parenthesis.
P14, Figure 6 caption: Rather “hatches” than “crosses”?
P17, L394: Is this shown in this study? Which section? Add a reference or on which place in the manuscript this is discussed. In Line 389 you mention a warming, but without a specific month
P18, Figure 9 caption: Same here as for the caption of Figure 6. Rather “hatches” than “crosses”.
P17, L405: “Discussion and reanalysis vertical residual circulation” sounds weird. I would suggest to name this section just “Discussion”.
P18, L429: It is not clear if you refer here to Fig. 1 in your manuscript or in Shine et al. (2003).
P19, L440: Add a reference for this statement
P19, L444: “Here” not clear. Do you mean in this study or in this section?
References: Journal names should be abbreviated. For some references it is done, but for some not. Note, for the reference of Simmons (2020) the journal and volume are missing.

Technical corrections:
P3, L82: Add “by” so that it reads “by covering”.
P3, L93: “last” -> “past” (?)
P7, L180: skip “models”
P7, L185: ERA-5 -> ERA5
P10, L274: omit “Appendix”, just writing “see Fig. A2” is sufficient.
P12, L307: omit also here “Appendix”.
P12, Figure 5 caption: MERRA-22 -> MERRA-2
P18, L424: It should read “Arblaster et al, 2014” and a space between the year and “and” is missing.
P18, L435: Add “by” so that it reads “……by somewhat weakening…”.
P19, L462: shows -> show
P20, L477: shows -> show
P20, Figure 10 caption: for three periods -> for the three time periods
P22, 517-521: Rather than “last accessed” I would suggest to write “last access”.

Best regards, Farahnaz Khosrawi

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AR by Mona Zolghadrshojaee on behalf of the Authors (24 Jul 2025) Author's response Author's tracked changes Manuscript

ED: Publish as is (25 Jul 2025) by Farahnaz Khosrawi

AR by Mona Zolghadrshojaee on behalf of the Authors (31 Jul 2025) Author's response Manuscript

Journal article(s) based on this preprint

07 Oct 2025

Shift in cold-point tropopause trends derived from radiosonde, satellite and reanalysis data

Mona Zolghadrshojaee, Susann Tegtmeier, Sean M. Davis, Robin Pilch Kedzierski, and Leopold Haimberger

Atmos. Chem. Phys., 25, 12213–12232, https://doi.org/10.5194/acp-25-12213-2025,https://doi.org/10.5194/acp-25-12213-2025, 2025

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Mona Zolghadrshojaee, Susann Tegtmeier, Sean M. Davis, Robin Pilch Kedzierski, and Leopold Haimberger

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Jun 2025	33	6	2	41
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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.

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The tropical tropopause layer (TTL) is a crucial region where the troposphere transitions into the stratosphere, influencing air mass transport. This study examines temperature trends in the TTL and lower stratosphere using data from weather balloons, satellites, and reanalysis datasets. We found cooling trends in the TTL from 1980–2001, followed by warming from 2002–2023. These shifts are linked to changes in atmospheric circulation and impact water vapor transport into the stratosphere.


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