Determination of Tropical Belt Widening Using Multiple GNSS Radio Occultation Measurements
- 1School of Remote Sensing and Geomatics Engineering, Nanjing University of Information Science and Technology, Nanjing, China
- 2National Research Institute of Astronomy and Geophysics-NRIAG, 11421- Helwan, Cairo, Egypt
- 3Shanghai Astronomical Observatory, Chinese Academy of Science, Shanghai, China
- 1School of Remote Sensing and Geomatics Engineering, Nanjing University of Information Science and Technology, Nanjing, China
- 2National Research Institute of Astronomy and Geophysics-NRIAG, 11421- Helwan, Cairo, Egypt
- 3Shanghai Astronomical Observatory, Chinese Academy of Science, Shanghai, China
Abstract. In the last decades, Global navigation satellite systems (GNSS) have provided an exceptional opportunity to retrieve atmospheric parameters globally through GNSS radio occultation (GNSS-RO). In this paper, data of 12 GNSS-RO missions from June 2001 to November 2020 with high resolution were used to investigate the possible widening of the tropical belt along with the probable drivers and impacts in both hemispheres. Applying both lapse rate tropopause (LRT) and cold point tropopause (CPT) definitions, the global tropopause height shows increase of approximately 36 m/decade and 60 m/decade, respectively. Moreover, the tropical edge latitude (TEL) estimated based on two tropopause height metrics, in the northern hemisphere (NH) and southern hemisphere (SH), are different from each other. For the first metric, subjective method, the tropical width from GNSS has expansion behavior in NH with ~ 0.41°/decade and a minor expansion in SH with ~ 0.08°/decade. In case of ECMWF Reanalysis v5 (ERA5) there is no significant contraction in both NH and SH. For Atmospheric Infrared Sounder (AIRS), there are expansion behavior in NH with ~ 0.34°/decade and strong contraction in SH with ~ −0.48°/decade. Using the second metric, objective method, the tropical width from GNSS has expansion in NH with ~ 0.13°/decade, and no significant expansion in SH. In case of ERA5, there is no significant signal in NH while SH has a minor contraction. AIRS has an expansion with ~ 0.13°/decade in NH, and strong contraction in SH with ~ −0.37°/decade. The variability of tropopause parameters (temperature and height) is maximum around the TEL locations at both hemispheres. The total column ozone (TCO) shows increasing rates globally, and the rate of increase at the SH is higher than that of the NH. There is a good agreement between the spatial and temporal patterns of TCO variability and the TEL location estimated from GNSS LRT height. Carbon dioxide (CO2), and Methane (CH4), the most important greenhouse gases (GHGs) and the main drivers of global warming, have a global increasing rate and the increasing rate of the NH is similar to that of the SH. The spatial pattern in the NH is located more pole ward than its equivalent at the SH. Both surface temperature and precipitation increase in time and have strong correlation with GNSS LRT height. Both show higher increasing rates at the NH, while the precipitation at the SH has slight decrease and the surface temperature increases. The surface temperature shows a spatial pattern with strong variability, which broadly agrees with the TEL locations. The spatial pattern of precipitation shows northward occurrence. In addition, Standardized Precipitation Evapotranspiration Index (SPEI) has no direct connection with the TEL behavior.
Mohamed Darrag et al.
Status: closed
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RC1: 'Comment on angeo-2021-67', Anonymous Referee #1, 11 Feb 2022
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AC1: 'Reply on RC1', Mohamed Darrag, 23 Feb 2022
The comment was uploaded in the form of a supplement: https://angeo.copernicus.org/preprints/angeo-2021-67/angeo-2021-67-AC1-supplement.pdf
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AC1: 'Reply on RC1', Mohamed Darrag, 23 Feb 2022
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RC2: 'Comment on angeo-2021-67', Anonymous Referee #2, 18 Mar 2022
Major comments
- The data of the atmospheric profiles came from very different GNSS-RO sources (Fig 1) and different time of missions. It means that accuracy, data time-rate, region of the atmosphere under RO-sounding very differ from one source (mission) to another. In turn, it may bring uncertainties and mistakes in the long lasting data interpreting. I would recommend to the authors to add correspondent explanation in Section 2 and in Conclusion section.
- In my opinion, there is luck of discussion of Fig 2-10. There is only list of facts with no even minimal comments. I suppose that minimal discussion for each figure is necessary, something like this: the results on Fig correspond (or contradict) to the physical model of the process (or the known results [Reference 1, Reference 2 et al.]). It can be explained by….. et al.
- In my opinion Conclusion section should consist of more detailed explanation of the unfolded trends in the tropopause height increasing. This is the main results of the manuscript which is important in the global weather forecast.
Minor comments
- Abstract: In my opinion Abstract is very long and difficult to catch the main idea of the research. All the numerical evaluations and its short discussion should be in the main text, but not in abstract. Abstract should be short and clear for readers. It should consists of following points: motivation; general list of means of data treatment (or theoretical analysis), experiment environment et al; main results and its novelty declaration comparing to the known results.
- Line 72 and Line 74: What do these “…reanalyses trends…” and “…different reanalyses…” mean?
- Line 236: Please check and correct it: “…is no significant correlation 0.21…”.
- Line 241: “global increasing trend of LRT height 241 of 36 m/decade”. Looking at the Fig 2 I see this trend for CPT but not for LPT. Please check it.
- Line 483: What do you mean here: ”there is no significant signal in the…”?
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AC2: 'Reply on RC2', Mohamed Darrag, 02 Apr 2022
The comment was uploaded in the form of a supplement: https://angeo.copernicus.org/preprints/angeo-2021-67/angeo-2021-67-AC2-supplement.pdf
Status: closed
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RC1: 'Comment on angeo-2021-67', Anonymous Referee #1, 11 Feb 2022
-
AC1: 'Reply on RC1', Mohamed Darrag, 23 Feb 2022
The comment was uploaded in the form of a supplement: https://angeo.copernicus.org/preprints/angeo-2021-67/angeo-2021-67-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Mohamed Darrag, 23 Feb 2022
-
RC2: 'Comment on angeo-2021-67', Anonymous Referee #2, 18 Mar 2022
Major comments
- The data of the atmospheric profiles came from very different GNSS-RO sources (Fig 1) and different time of missions. It means that accuracy, data time-rate, region of the atmosphere under RO-sounding very differ from one source (mission) to another. In turn, it may bring uncertainties and mistakes in the long lasting data interpreting. I would recommend to the authors to add correspondent explanation in Section 2 and in Conclusion section.
- In my opinion, there is luck of discussion of Fig 2-10. There is only list of facts with no even minimal comments. I suppose that minimal discussion for each figure is necessary, something like this: the results on Fig correspond (or contradict) to the physical model of the process (or the known results [Reference 1, Reference 2 et al.]). It can be explained by….. et al.
- In my opinion Conclusion section should consist of more detailed explanation of the unfolded trends in the tropopause height increasing. This is the main results of the manuscript which is important in the global weather forecast.
Minor comments
- Abstract: In my opinion Abstract is very long and difficult to catch the main idea of the research. All the numerical evaluations and its short discussion should be in the main text, but not in abstract. Abstract should be short and clear for readers. It should consists of following points: motivation; general list of means of data treatment (or theoretical analysis), experiment environment et al; main results and its novelty declaration comparing to the known results.
- Line 72 and Line 74: What do these “…reanalyses trends…” and “…different reanalyses…” mean?
- Line 236: Please check and correct it: “…is no significant correlation 0.21…”.
- Line 241: “global increasing trend of LRT height 241 of 36 m/decade”. Looking at the Fig 2 I see this trend for CPT but not for LPT. Please check it.
- Line 483: What do you mean here: ”there is no significant signal in the…”?
-
AC2: 'Reply on RC2', Mohamed Darrag, 02 Apr 2022
The comment was uploaded in the form of a supplement: https://angeo.copernicus.org/preprints/angeo-2021-67/angeo-2021-67-AC2-supplement.pdf
Mohamed Darrag et al.
Mohamed Darrag et al.
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