the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 03 Sep 2025
Development and Validation of a New Ozone Dataset Using Complete Data Fusion of MIPAS and IASI Observations: A Step Towards Understanding Stratospheric Ozone Intrusions in the Himalayan Region
Abstract. We present a new ozone dataset generated using the Complete Data Fusion (CDF) algorithm, which combines limb observations from MIPAS-ENVISAT along with nadir observations from IASI during their overlapping operational period (2008–2011). The fusion aims to enhance ozone profile information in the Upper Troposphere–Lower Stratosphere (UTLS), particularly over the Himalayas—a key region for stratospheric intrusion events. The fused dataset, mapped onto the IASI- MetOp grid, includes ozone partial columns with associated uncertainty estimates (covariance matrices, averaging kernels, and a priori profiles). After tuning the algorithm on 2008 data, the product was validated for the 2009–2011 period against ozonesondes from WOUDC stations across multiple latitude bands. Results show that the fused profiles improve vertical information content (degrees of freedom) and reduce uncertainty, successfully propagating MIPAS information to lower altitudes even in regions lacking direct limb observations. While the dataset initially exhibited altitude- and latitude-dependent biases, primarily inherited from IASI, these were significantly reduced through bias correction. The final product is suitable for data assimilation and model evaluation, offering valuable support for atmospheric reanalyses and studies of troposphere–stratosphere exchange processes.
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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
(8091 KB)
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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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Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2025-3231', Anonymous Referee #1, 20 Sep 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3231/egusphere-2025-3231-RC1-supplement.pdfCitation: https://doi.org/
10.5194/egusphere-2025-3231-RC1 -
AC2: 'Reply on RC1', Liliana Guidetti, 19 Nov 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3231/egusphere-2025-3231-AC2-supplement.pdf
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AC3: 'Reply on RC1', Liliana Guidetti, 19 Nov 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3231/egusphere-2025-3231-AC3-supplement.pdf
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AC2: 'Reply on RC1', Liliana Guidetti, 19 Nov 2025
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RC2: 'Comment on egusphere-2025-3231', Anonymous Referee #2, 22 Sep 2025
This manuscript presents the development and validation of a new ozone dataset, generated by applying a Complete Data Fusion (CDF) algorithm to combine limb observations from MIPAS with nadir observations from IASI for the 2008–2011 period. Overall, the authors have done good job in detailing the methodology, including the tuning process across nine different configurations. This systematic approach highlights the trade-offs in terms of bias, degrees of freedom (DOFs), and retrieval errors. The validation against ozone sonde data spans multiple years and latitudinal bands, and the scientific motivation is clear: the need for high-resolution data in the Upper Troposphere–Lower Stratosphere (UTLS) to better understand processes such as stratospheric intrusions, particularly in complex regions like the Himalayas.
To some extent, the authors clearly demonstrate the improvements of the fused product relative to ozone sonde measurement. Their key finding is that that the new dataset offers higher DOFs and reduced uncertainty compared to individual MIPAS and IASI retrievals, especially in the UTLS region. The manuscript illustrates that stratospheric ozone profile information from MIPAS helps constrain the ozone profile at lower altitudes. Moreover, the authors carefully analyse the altitude- and latitude-dependent biases IASI data and apply a bias correction that significantly enhances the quality of the final product, making it more suitable for scientific applications.
While the manuscript is relatively well rounded, a few suggestions could further enhance its impact. First, the dataset covers a relatively short period (2008–2011), which may limit its utility for chemical modelers for the chemistry/dynamics related evaluations. To better showcase the new data sets unique value, I strongly recommend including a specific case study—such as a well-documented stratospheric intrusion event—where the fused product demonstrates improved agreement with ozone sonde data compared to reanalyses like CAMS or ERA5. Additionally, given the manuscript’s focus on Stratosphere-Troposphere Exchange (STE) in the Himalayan region, it is noteworthy that the ozone sonde stations shown in Figure 1 are predominantly located in Europe and the United States. Incorporating independent ozone sonde data from the Himalayan region would allow for a more targeted evaluation of the fused dataset in its primary area of interest. Finally, I strongly encourage the authors to adopt an open-data policy. Making the dataset publicly available would facilitate broader evaluation and application by the research community, thereby maximizing the impact of this important work. The current statement that data is available upon request may limit its accessibility and utility.
Citation: https://doi.org/10.5194/egusphere-2025-3231-RC2 -
AC1: 'Reply on RC2', Liliana Guidetti, 19 Nov 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3231/egusphere-2025-3231-AC1-supplement.pdf
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AC1: 'Reply on RC2', Liliana Guidetti, 19 Nov 2025
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2025-3231', Anonymous Referee #1, 20 Sep 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3231/egusphere-2025-3231-RC1-supplement.pdf
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AC2: 'Reply on RC1', Liliana Guidetti, 19 Nov 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3231/egusphere-2025-3231-AC2-supplement.pdf
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AC3: 'Reply on RC1', Liliana Guidetti, 19 Nov 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3231/egusphere-2025-3231-AC3-supplement.pdf
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AC2: 'Reply on RC1', Liliana Guidetti, 19 Nov 2025
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RC2: 'Comment on egusphere-2025-3231', Anonymous Referee #2, 22 Sep 2025
This manuscript presents the development and validation of a new ozone dataset, generated by applying a Complete Data Fusion (CDF) algorithm to combine limb observations from MIPAS with nadir observations from IASI for the 2008–2011 period. Overall, the authors have done good job in detailing the methodology, including the tuning process across nine different configurations. This systematic approach highlights the trade-offs in terms of bias, degrees of freedom (DOFs), and retrieval errors. The validation against ozone sonde data spans multiple years and latitudinal bands, and the scientific motivation is clear: the need for high-resolution data in the Upper Troposphere–Lower Stratosphere (UTLS) to better understand processes such as stratospheric intrusions, particularly in complex regions like the Himalayas.
To some extent, the authors clearly demonstrate the improvements of the fused product relative to ozone sonde measurement. Their key finding is that that the new dataset offers higher DOFs and reduced uncertainty compared to individual MIPAS and IASI retrievals, especially in the UTLS region. The manuscript illustrates that stratospheric ozone profile information from MIPAS helps constrain the ozone profile at lower altitudes. Moreover, the authors carefully analyse the altitude- and latitude-dependent biases IASI data and apply a bias correction that significantly enhances the quality of the final product, making it more suitable for scientific applications.
While the manuscript is relatively well rounded, a few suggestions could further enhance its impact. First, the dataset covers a relatively short period (2008–2011), which may limit its utility for chemical modelers for the chemistry/dynamics related evaluations. To better showcase the new data sets unique value, I strongly recommend including a specific case study—such as a well-documented stratospheric intrusion event—where the fused product demonstrates improved agreement with ozone sonde data compared to reanalyses like CAMS or ERA5. Additionally, given the manuscript’s focus on Stratosphere-Troposphere Exchange (STE) in the Himalayan region, it is noteworthy that the ozone sonde stations shown in Figure 1 are predominantly located in Europe and the United States. Incorporating independent ozone sonde data from the Himalayan region would allow for a more targeted evaluation of the fused dataset in its primary area of interest. Finally, I strongly encourage the authors to adopt an open-data policy. Making the dataset publicly available would facilitate broader evaluation and application by the research community, thereby maximizing the impact of this important work. The current statement that data is available upon request may limit its accessibility and utility.
Citation: https://doi.org/10.5194/egusphere-2025-3231-RC2 -
AC1: 'Reply on RC2', Liliana Guidetti, 19 Nov 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3231/egusphere-2025-3231-AC1-supplement.pdf
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AC1: 'Reply on RC2', Liliana Guidetti, 19 Nov 2025
Peer review completion
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Liliana Guidetti
Erika Brattich
Simone Ceccherini
Michaela Imelda Hegglin
Piera Raspollini
Cecilia Tirelli
Ugo Cortesi
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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