MIPAS observations of ozone in the middle atmosphere
In this paper we describe the stratospheric and mesospheric ozone (version V5r_O3_m22) distributions retrieved from MIPAS observations in the three middle atmosphere modes (MA, NLC, and UA) taken with an unapodized spectral resolution of 0.0625 cm<sup>−1</sup> from 2005 until April 20...
Main Authors: | , , , , , , , , , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2018-04-01
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Series: | Atmospheric Measurement Techniques |
Online Access: | https://www.atmos-meas-tech.net/11/2187/2018/amt-11-2187-2018.pdf |
Summary: | In this paper we describe the stratospheric and mesospheric
ozone (version V5r_O3_m22) distributions retrieved from
MIPAS observations in the three middle atmosphere modes (MA, NLC, and UA) taken with an unapodized spectral resolution of
0.0625 cm<sup>−1</sup> from 2005 until April 2012. O<sub>3</sub> is retrieved from microwindows in the 14.8 and
10 µm spectral regions and requires non-local thermodynamic equilibrium (non-LTE) modelling of the O<sub>3</sub> <i>v</i><sub>1</sub> and <i>v</i><sub>3</sub> vibrational
levels. Ozone is reliably retrieved from 20 km in the MA mode (40 km for UA and NLC) up to ∼ 105 km during dark
conditions and up to ∼ 95 km during illuminated conditions. Daytime MIPAS O<sub>3</sub> has an average vertical
resolution of 3–4 km below 70 km, 6–8 km at 70–80 km, 8–10 km at 80–90, and 5–7 km at the secondary maximum
(90–100 km). For nighttime conditions, the vertical resolution is similar below 70 km and better in the upper
mesosphere and lower thermosphere: 4–6 km at 70–100 km, 4–5 km at the secondary maximum, and 6–8 km at
100–105 km. The noise error for daytime conditions is typically smaller than 2 % below 50 km, 2–10 % between
50 and 70 km, 10–20 % at 70–90 km, and ∼ 30 % above 95 km. For nighttime, the noise errors are very
similar below around 70 km but significantly smaller above, being 10–20 % at 75–95 km, 20–30 % at
95–100 km,
and larger than 30 % above 100 km. The additional major O<sub>3</sub> errors are the spectroscopic data uncertainties
below 50 km (10–12 %) and the non-LTE and temperature errors above 70 km. The validation performed suggests that
the spectroscopic errors below 50 km, mainly caused by the O<sub>3</sub> air-broadened half-widths of the <i>v</i><sub>2</sub> band, are
overestimated. The non-LTE error (including the uncertainty of atomic oxygen in nighttime) is relevant only above
∼ 85 km with values of 15–20 %. The temperature error varies from ∼ 3 % up to 80 km to 15–20 %
near 100 km. Between 50 and 70 km, the pointing and spectroscopic errors are the dominant uncertainties. The validation
performed in comparisons with SABER, GOMOS, MLS, SMILES, and ACE-FTS shows that MIPAS O<sub>3</sub> has an accuracy better
than 5 % at and below 50 km, with a positive bias of a few percent. In the 50–75 km region, MIPAS O<sub>3</sub> has
a positive bias of ≈ 10 %, which is possibly caused in part by O<sub>3</sub> spectroscopic errors in the
10 µm region. Between 75 and 90 km, MIPAS nighttime O<sub>3</sub> is in agreement with other instruments by
10 %, but for daytime the agreement is slightly larger, ∼ 10–20 %. Above 90 km, MIPAS daytime O<sub>3</sub>
is in agreement with other instruments by 10 %. At night, however, it shows a positive bias increasing from
10 % at 90 km to 20 % at 95–100 km, the latter of which is attributed to the large atomic oxygen abundance
used. We also present MIPAS O<sub>3</sub> distributions as function of altitude, latitude, and time, showing the major
O<sub>3</sub> features in the middle and upper mesosphere. In addition to the rapid diurnal variation due to photochemistry,
the data also show apparent signatures of the diurnal migrating tide during both day- and nighttime, as well as the
effects of the semi-annual oscillation above ∼ 70 km in the tropics and mid-latitudes. The tropical daytime
O<sub>3</sub> at 90 km shows a solar signature in phase with the solar cycle. |
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ISSN: | 1867-1381 1867-8548 |