MIPAS ozone retrieval version 8: middle-atmosphere measurements
<p>We present a new version of <span class="inline-formula">O<sub>3</sub></span> data retrieved from the three Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) observation modes that we refer to for simplicity as the modes of the middle atmosp...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-11-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/16/5609/2023/amt-16-5609-2023.pdf |
| Summary: | <p>We present a new version of <span class="inline-formula">O<sub>3</sub></span> data retrieved from the three Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) observation modes that we refer to for simplicity as the modes of the middle atmosphere (middle atmosphere, MA; upper atmosphere, UA; and noctilucent cloud, NLC). The <span class="inline-formula">O<sub>3</sub></span> profiles cover altitudes from 20 up to 100 <span class="inline-formula">km</span> for the daytime and up to 105 <span class="inline-formula">km</span> at nighttime, for all latitudes, and the period 2005 until 2012. The data have been obtained with the IMK–IAA (Institute of Meteorology and Climate Research and Instituto de Astrofísica de Andalucía) MIPAS level-2 data processor and are based on ESA version-8 re-calibrated radiance spectra with improved temporal stability. The processing included several improvements with respect to the previous version, such as the consistency of the microwindows and spectroscopic data with those used in the nominal-mode V8R data, the <span class="inline-formula">O<sub>3</sub></span> a priori profiles, and updates of the non-local thermodynamic equilibrium (non-LTE) parameters and the nighttime atomic oxygen. In particular, the collisional relaxation of <span class="inline-formula">O<sub>3</sub></span>(<span class="inline-formula"><i>v</i><sub>1</sub></span>,<span class="inline-formula"><i>v</i><sub>3</sub></span>) by the atomic oxygen was reduced by a factor of 2 in order to obtain a better agreement of nighttime mesospheric <span class="inline-formula">O<sub>3</sub></span> with “non-LTE-free” measurements. Random errors are dominated by the measurement noise with 1<span class="inline-formula"><i>σ</i></span> values for single profiles for the daytime of <span class="inline-formula"><</span> 5 % below <span class="inline-formula">∼</span> 60 <span class="inline-formula">km</span>, 5 %–10 % between 60 and 70 <span class="inline-formula">km</span>, 10 %–20 % at 70–90 <span class="inline-formula">km</span>, and about 30 % at 95 <span class="inline-formula">km</span>. For nighttime, they are very similar below 70 <span class="inline-formula">km</span> but smaller above (10 %–20 % at 75–95 <span class="inline-formula">km</span>, 20 %–30 % at 95–100 <span class="inline-formula">km</span> and larger than 30 % above 100 <span class="inline-formula">km</span>). The systematic error is <span class="inline-formula">∼</span> 6 % below <span class="inline-formula">∼</span> 60 <span class="inline-formula">km</span> (dominated by uncertainties in spectroscopic data) and 8 %–12 % above <span class="inline-formula">∼</span> 60 <span class="inline-formula">km</span>, mainly caused by non-LTE uncertainties. The systematic errors in the 80–100 <span class="inline-formula">km</span> range are significantly smaller than in the previous version. The major differences with respect to the previous version are as follows: (1) the new retrievals provide <span class="inline-formula">O<sub>3</sub></span> abundances in the 20–50 <span class="inline-formula">km</span> altitude range that are larger by about 2 %–5 % (0.2–0.5 <span class="inline-formula">ppmv</span>); (2) <span class="inline-formula">O<sub>3</sub></span> abundances were reduced by <span class="inline-formula">∼</span> 2 %–4 % between 50 and 60 <span class="inline-formula">km</span> in the tropics and mid-latitudes; (3) <span class="inline-formula">O<sub>3</sub></span> abundances in the nighttime <span class="inline-formula">O<sub>3</sub></span> minimum just below 80 <span class="inline-formula">km</span> were reduced, leading to a more realistic diurnal variation; (4) daytime <span class="inline-formula">O<sub>3</sub></span> concentrations in the secondary maximum at the tropical and middle latitudes (<span class="inline-formula">∼</span> 40 %, 0.2–0.3 <span class="inline-formula">ppmv</span>) were larger; and (5) nighttime <span class="inline-formula">O<sub>3</sub></span> abundances in the secondary maximum were reduced by 10 %–30 %. The <span class="inline-formula">O<sub>3</sub></span> profiles retrieved from the nominal mode (NOM) and the middle-atmosphere modes are fully consistent in their common altitude range (20–70 <span class="inline-formula">km</span>). Only at 60–70 <span class="inline-formula">km</span> does daytime <span class="inline-formula">O<sub>3</sub></span> of NOM seem to be larger than that of MA/UA by 2 %–10 %. Compared to other satellite instruments, MIPAS seems to have a positive bias of 5 %–8 % below 70 <span class="inline-formula">km</span>. Noticeably, the new version of MIPAS data agrees much better than before with all instruments in the upper mesosphere–lower thermosphere, reducing the differences from <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M46" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>∼</mo><mo>±</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="22pt" height="8pt" class="svg-formula" dspmath="mathimg" md5hash="98e83d48da1eccbd58399d2b2d880fb0"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-16-5609-2023-ie00001.svg" width="22pt" height="8pt" src="amt-16-5609-2023-ie00001.png"/></svg:svg></span></span> 20 % to <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M47" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>∼</mo><mo>±</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="22pt" height="8pt" class="svg-formula" dspmath="mathimg" md5hash="339d4643f35a23e68b14d5655a4fc756"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-16-5609-2023-ie00002.svg" width="22pt" height="8pt" src="amt-16-5609-2023-ie00002.png"/></svg:svg></span></span> 10 %. Further, the diurnal variation in <span class="inline-formula">O<sub>3</sub></span> in the upper mesosphere (near 80 <span class="inline-formula">km</span>) has been significantly improved.</p> |
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| ISSN: | 1867-1381 1867-8548 |