Homogenization of the Observatoire de Haute Provence electrochemical concentration cell (ECC) ozonesonde data record: comparison with lidar and satellite observations
<p>The Observatoire de Haute Provence (OHP) weekly electrochemical concentration cell (ECC) ozonesonde data have been homogenized for the period 1991–2021 according to the recommendations of the Ozonesonde Data Quality Assessment (O3S-DQA) panel. The assessment of the ECC homogenization benefi...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-05-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/15/3105/2022/amt-15-3105-2022.pdf |
| Summary: | <p>The Observatoire de Haute Provence (OHP) weekly electrochemical concentration cell (ECC) ozonesonde data have been homogenized for the period 1991–2021 according to the recommendations of the Ozonesonde Data Quality Assessment (O3S-DQA) panel. The assessment of the ECC homogenization
benefit has been carried out using comparisons with other ozone-measuring ground-based instruments at the same station (lidar, surface measurements)
and with colocated satellite observations of the <span class="inline-formula">O<sub>3</sub></span> vertical profile by Microwave Limb Sounder (MLS). The major differences between
uncorrected and homogenized ECC data are related to a change of ozonesonde type in 1997, removal of the pressure dependency of the ECC background
current and correction of internal pump temperature. The original 3–4 <span class="inline-formula">ppbv</span> positive bias between ECC and lidar in the troposphere is
corrected with the homogenization. The ECC 30-year trends of the seasonally adjusted ozone concentrations are also significantly improved in both
the troposphere and the stratosphere after the ECC homogenization, as shown by the ECC/lidar or ECC/surface ozone trend comparisons. A <span class="inline-formula">−0.19</span> % yr<span class="inline-formula"><sup>−1</sup></span> negative trend of the normalization factor (<span class="inline-formula"><i>N</i><sub>T</sub></span>) calculated using independent measurements of the total ozone column (TOC) at
OHP disappears after homogenization of the ECC data. There is, however, a remaining <span class="inline-formula">−3.7</span> % negative bias in the TOC which is likely related to
an underestimate of the ECC concentrations in the stratosphere above 50 <span class="inline-formula">hPa</span>. Differences between TOC measured by homogenized ECC and
satellite observations show a smaller bias of <span class="inline-formula">−1</span> %. Comparisons between homogenized ECC and OHP stratospheric lidar and MLS observations below 26 <span class="inline-formula">km</span> are slightly negative (<span class="inline-formula">−2</span> %) or positive (<span class="inline-formula">+2</span> %), respectively. The comparisons with both lidar and satellite observations
suggest that homogenization increases the negative bias of the ECC to values lower than <span class="inline-formula">−6</span> % above 28 <span class="inline-formula">km</span>. The reason for this bias is still unclear, but a possible explanation might be related to freezing or evaporation of the sonde solution in the stratosphere.</p> |
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| ISSN: | 1867-1381 1867-8548 |