A tropopause-related climatological a priori profile for IASI-SOFRID ozone retrievals: improvements and validation
<p>The MetOp/Infrared Atmospheric Sounding Interferometer (IASI) instruments have provided data for operational meteorology and document atmospheric composition since 2007. IASI ozone (<span class="inline-formula">O<sub>3</sub></span>) data have been used exte...
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-10-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/13/5237/2020/amt-13-5237-2020.pdf |
| _version_ | 1818307082927996928 |
|---|---|
| author | B. Barret E. Emili E. Le Flochmoen |
| author_facet | B. Barret E. Emili E. Le Flochmoen |
| author_sort | B. Barret |
| collection | DOAJ |
| description | <p>The MetOp/Infrared Atmospheric Sounding Interferometer (IASI) instruments have provided data for operational meteorology and
document atmospheric composition since 2007. IASI ozone (<span class="inline-formula">O<sub>3</sub></span>) data have been used
extensively to characterize the seasonal and interannual variabilities and the evolution
of tropospheric <span class="inline-formula">O<sub>3</sub></span> at the global scale. SOftware for a Fast Retrieval of IASI Data (SOFRID) is a fast retrieval algorithm that
provides IASI <span class="inline-formula">O<sub>3</sub></span> profiles for the whole IASI period.
Until now, SOFRID <span class="inline-formula">O<sub>3</sub></span> retrievals (v1.5 and v1.6) were performed with a
single a priori profile, which resulted in important biases and probably a
too-low variability. For the first time, we have implemented a comprehensive
dynamical a priori profile for spaceborne <span class="inline-formula">O<sub>3</sub></span> retrievals which takes the pixel location, time
and tropopause height into account for SOFRID-O3 v3.5
retrievals. In the
present study, we validate SOFRID-O3 v1.6 and v3.5 with electrochemical concentration cell (ECC) ozonesonde profiles
from the global World Ozone and Ultraviolet Radiation Data Centre (WOUDC) database for the 2008–2017 period. Our validation is
based on a thorough statistical analysis using Taylor diagrams. Furthermore, we
compare our retrievals with ozonesonde profiles both smoothed by the IASI averaging kernels and raw.
This methodology is essential to
evaluate the inherent usefulness of the retrievals to assess <span class="inline-formula">O<sub>3</sub></span> variability and trends. The use of
a dynamical a priori profile largely improves the retrievals concerning two main
aspects: (i) it corrects high biases for low-tropospheric <span class="inline-formula">O<sub>3</sub></span> regions such as
the Southern
Hemisphere, and (ii) it increases the retrieved <span class="inline-formula">O<sub>3</sub></span> variability, leading to a
better agreement with ozonesonde data. Concerning upper troposphere–lower stratosphere (UTLS) and stratospheric <span class="inline-formula">O<sub>3</sub></span>,
the improvements are less important and the biases are very similar for both
versions. The SOFRID tropospheric ozone columns (TOCs)
display no significant drifts (<span class="inline-formula"><2.5</span> %) for the Northern Hemisphere
and significant negative ones (9.5 % for v1.6 and 4.3 % for v3.5) for the Southern Hemisphere. We
have compared our validation results to those of the Fast Optimal Retrievals on Layers for IASI (FORLI)
retrieval software from the
literature for smoothed ozonesonde data only. This comparison highlights three
main differences:
(i) FORLI retrievals contain more theoretical information about tropospheric <span class="inline-formula">O<sub>3</sub></span>
than SOFRID;
(ii) root mean square differences (RMSDs) are smaller and correlation
coefficients are higher for SOFRID than for FORLI; (iii) in the Northern
Hemisphere, the 2010 jump detected in FORLI TOCs is not
present in SOFRID.</p> |
| first_indexed | 2024-12-13T06:52:44Z |
| format | Article |
| id | doaj.art-bcacae62d7d243af819bcab370ec7c90 |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-12-13T06:52:44Z |
| publishDate | 2020-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-bcacae62d7d243af819bcab370ec7c902022-12-21T23:56:07ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482020-10-01135237525710.5194/amt-13-5237-2020A tropopause-related climatological a priori profile for IASI-SOFRID ozone retrievals: improvements and validationB. Barret0E. Emili1E. Le Flochmoen2Laboratoire d'Aérologie/OMP, Université de Toulouse, Toulouse, FranceCECI, Université de Toulouse, CERFACS, CNRS, Toulouse, FranceLaboratoire d'Aérologie/OMP, Université de Toulouse, Toulouse, France<p>The MetOp/Infrared Atmospheric Sounding Interferometer (IASI) instruments have provided data for operational meteorology and document atmospheric composition since 2007. IASI ozone (<span class="inline-formula">O<sub>3</sub></span>) data have been used extensively to characterize the seasonal and interannual variabilities and the evolution of tropospheric <span class="inline-formula">O<sub>3</sub></span> at the global scale. SOftware for a Fast Retrieval of IASI Data (SOFRID) is a fast retrieval algorithm that provides IASI <span class="inline-formula">O<sub>3</sub></span> profiles for the whole IASI period. Until now, SOFRID <span class="inline-formula">O<sub>3</sub></span> retrievals (v1.5 and v1.6) were performed with a single a priori profile, which resulted in important biases and probably a too-low variability. For the first time, we have implemented a comprehensive dynamical a priori profile for spaceborne <span class="inline-formula">O<sub>3</sub></span> retrievals which takes the pixel location, time and tropopause height into account for SOFRID-O3 v3.5 retrievals. In the present study, we validate SOFRID-O3 v1.6 and v3.5 with electrochemical concentration cell (ECC) ozonesonde profiles from the global World Ozone and Ultraviolet Radiation Data Centre (WOUDC) database for the 2008–2017 period. Our validation is based on a thorough statistical analysis using Taylor diagrams. Furthermore, we compare our retrievals with ozonesonde profiles both smoothed by the IASI averaging kernels and raw. This methodology is essential to evaluate the inherent usefulness of the retrievals to assess <span class="inline-formula">O<sub>3</sub></span> variability and trends. The use of a dynamical a priori profile largely improves the retrievals concerning two main aspects: (i) it corrects high biases for low-tropospheric <span class="inline-formula">O<sub>3</sub></span> regions such as the Southern Hemisphere, and (ii) it increases the retrieved <span class="inline-formula">O<sub>3</sub></span> variability, leading to a better agreement with ozonesonde data. Concerning upper troposphere–lower stratosphere (UTLS) and stratospheric <span class="inline-formula">O<sub>3</sub></span>, the improvements are less important and the biases are very similar for both versions. The SOFRID tropospheric ozone columns (TOCs) display no significant drifts (<span class="inline-formula"><2.5</span> %) for the Northern Hemisphere and significant negative ones (9.5 % for v1.6 and 4.3 % for v3.5) for the Southern Hemisphere. We have compared our validation results to those of the Fast Optimal Retrievals on Layers for IASI (FORLI) retrieval software from the literature for smoothed ozonesonde data only. This comparison highlights three main differences: (i) FORLI retrievals contain more theoretical information about tropospheric <span class="inline-formula">O<sub>3</sub></span> than SOFRID; (ii) root mean square differences (RMSDs) are smaller and correlation coefficients are higher for SOFRID than for FORLI; (iii) in the Northern Hemisphere, the 2010 jump detected in FORLI TOCs is not present in SOFRID.</p>https://amt.copernicus.org/articles/13/5237/2020/amt-13-5237-2020.pdf |
| spellingShingle | B. Barret E. Emili E. Le Flochmoen A tropopause-related climatological a priori profile for IASI-SOFRID ozone retrievals: improvements and validation Atmospheric Measurement Techniques |
| title | A tropopause-related climatological a priori profile for IASI-SOFRID ozone retrievals: improvements and validation |
| title_full | A tropopause-related climatological a priori profile for IASI-SOFRID ozone retrievals: improvements and validation |
| title_fullStr | A tropopause-related climatological a priori profile for IASI-SOFRID ozone retrievals: improvements and validation |
| title_full_unstemmed | A tropopause-related climatological a priori profile for IASI-SOFRID ozone retrievals: improvements and validation |
| title_short | A tropopause-related climatological a priori profile for IASI-SOFRID ozone retrievals: improvements and validation |
| title_sort | tropopause related climatological a priori profile for iasi sofrid ozone retrievals improvements and validation |
| url | https://amt.copernicus.org/articles/13/5237/2020/amt-13-5237-2020.pdf |
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