Variations of Arctic winter ozone from the LIMS Level 3 dataset

The Nimbus 7 limb infrared monitor of the stratosphere (LIMS) instrument operated from October 25, 1978, through May 28, 1979. Its Version 6 (V6) profiles and their Level 3 or zonal Fourier coefficient products have been characterized and archived in 2008 and in 2011, respectively. This paper focuses on the value and use of daily ozone maps from Level 3, based on a gridding of its zonal coefficients. We present maps of V6 ozone on pressure surfaces and compare them with several rocket-borne chemiluminescent ozone measurements that extend into the lower mesosphere. Daily, synoptic maps of V6 ozone and temperature illustrate that they are an important aid in interpreting satellite limb-infrared emission versus local measurements, especially when they occur during dynamically active periods of northern hemisphere winter. We then show a sequence of V6 maps of upper stratospheric ozone, spanning the minor stratospheric warmings of late January and early February 1979. The map sequence of V6 geopotential height reveals how ozone was changing in the vortex and at the centers of adjacent anticyclones. We also report on zonal variations of the tertiary ozone maximum of the upper mesosphere and its associated temperature fields during winter. These several examples provide a guide to researchers for further exploratory analyses of middle atmosphere ozone from LIMS.

Solar cycle modulation of nighttime ozone near the mesopause as observed by MLS

<p>Solar 11-year cycle variations of nighttime ozone near the secondary ozone maximum layer are analyzed with Aura Microwave Limb Sounder (MLS) observations since 2004 that covers complete solar cycle 24. Produced primarily from the recombination of molecular oxygen (O<sub>2</sub>) with single oxygen (O) transported from the lower thermosphere, the mesospheric nighttime ozone concentration is proportional to single oxygen density [O], of which the latter is modulated by UV solar cycle variations. MLS nighttime ozone and Solar Radiation and Climate Experiment (SORCE) Solar-Stellar Irradiance Comparison Experiment (SOLSTICE) measured UV show a positive correlation in-phase with the solar cycle. The nighttime ozone correlates strongly with temperature but not monotonously positive nor negative. The slope and sign of the correlation depend on location and season. They are positively correlated in general except for the boreal winter high latitudes.  Because the nighttime [O<sub>3</sub>] depends strongly on [O] in the upper mesosphere, it is expected the nighttime [O<sub>3</sub>] would follow the [O] distributions, producing similar diurnal, seasonal, and solar-cycle variations, as well as latitudinal distributions as observed in Carbon Monoxide (CO) in the upper mesosphere.</p>

Solar activity influence on the ozone vertical distribution from SBUV data

<p>Ozone content in the terrestrial atmosphere is dependent on chemical and dynamical factors including catalytic destruction under the influence of chlorine and bromine, Brewer–Dobson circulation, and large-scale atmospheric waves. The appearance of ozone molecules in the stratosphere is caused by solar ultraviolet radiation as well. Therefore solar activity variations can influence ozone content. The 11-year solar cycle had been earlier identified in the upper stratosphere. Satellite ozone observations were begun from the 1970s are almost continuous from 1979 including the vertical ozone distribution, in particular with the use of Solar Backscattered UltraViolet (SBUV) instruments. These data cover the troposphere and stratosphere layers, from the surface to near 50 km. Vertical ozone distribution over the Ukrainian Antarctic station Akademik Vernadsky (65.25°S, 64.27°W) and in the corresponding latitudinal range 60–65°S is studied in this work with the following analysis of possible solar activity display in other latitudinal belts. Sunspot numbers have been considered as the simplest characteristics of solar activity. We have considered SBUV yearly data paying main attention to the time range from 1979 when the measurements are most reliable. Periodicity in the series of ozone layer content has been studied with use of wavelet transform. Processing of the SBUV data over Vernadsky has shown a dominating period near 10–11 years at the heights 18–31 km. In the troposphere and lower stratosphere, this period is unclear. A similar situation is observed above 31 km indicating the upper altitudinal threshold in the presence of the 10–11-year periodicity in the ozone data. The solar cycle influence on the ozone vertical distribution in the Antarctic region has been studied. From our analysis, the solar cycle plays an important role in the decadal variability of the mid-stratospheric ozone over Vernadsky Station with decrease of the effect both in the troposphere – lower stratosphere and in the upper stratosphere. A similar analysis is also realized for zonal mean ozone at the 60–65°S latitudes belt and for the region of zonal ozone maximum (Casey), where the solar cycle was indicated at the heights 31–37 km. Thus, zonal asymmetry in the heights of the maximum solar cycle effect in the Antarctic ozone exists. Periods close to 11 years are observed in the lower stratosphere of equatorial latitudes exhibiting seasonal dependency. At altitudes, 25–30 km, the southern stratosphere has more evident signs of solar cycle periods than the northern one. The summer upper stratosphere with a high flux of direct solar radiation is also a region with prominent quasi-11 year periods. In sum, three main regions with solar activity influence (tropical lower stratosphere, west Antarctic middle stratosphere, and east Antarctic upper stratosphere) are identified. The asymmetry between solar cycle influence (i) in the northern and southern hemisphere mid-stratosphere and (ii) zonal ozone maximum and minimum over Antarctica is denoted for the first time.</p><p>This work was partly supported by the project 19BF051-08 Taras Shevchenko National University of Kyiv and by the International Center of Future Science, Jilin University.</p>

Comparison of ozone profiles and influences from the tertiary ozone maximum in the night-to-day ratio above Switzerland

Stratospheric and middle-mesospheric ozone profiles above Bern, Switzerland (46.95° N, 7.44° E; 577 m) have been continually measured by the GROMOS (GROund-based Millimeter-wave Ozone Spectrometer) microwave radiometer since 1994. GROMOS is part of the Network for the Detection of Atmospheric Composition Change (NDACC). A new version of the ozone profile retrievals has been developed with the aim of improving the altitude range of retrieval profiles. GROMOS profiles from this new retrieval version have been compared to coincident ozone profiles obtained by the satellite limb sounder Aura Microwave Limb Sounder (MLS). The study covers the stratosphere and middle mesosphere from 50 to 0.05 hPa (from 21 to 70 km) and extends over the period from July 2009 to November 2016, which results in more than 2800 coincident profiles available for the comparison. On average, GROMOS and MLS comparisons show agreement generally over 20 % in the lower stratosphere and within 2 % in the middle and upper stratosphere for both daytime and nighttime, whereas in the mesosphere the mean relative difference is below 40 % during the daytime and below 15 % during the nighttime. In addition, we have observed the annual variation in nighttime ozone in the middle mesosphere, at 0.05 hPa (70 km), characterized by the enhancement of ozone during wintertime for both ground-based and space-based measurements. This behaviour is related to the middle-mesospheric maximum in ozone (MMM).

Comparison of ozone profiles and influences from the tertiary ozone maximum in the night-to-day ratio above Switzerland

Stratospheric and middle mesospheric ozone profiles have been continually measured by the GROMOS (GROund-based Millimeter-wave Ozone Spectrometer) microwave radiometer since 1994 above Bern, Switzerland (46.95° N, 7.44° E, 577 m). GROMOS is part of the Network for the Detection of Atmospheric Composition Change (NDACC). A new version for the retrieval of ozone profiles has been developed with the aim to improve the altitude range of retrieval profiles. GROMOS profiles from this new retrieval version have been compared to coincident ozone profiles obtained by the satellite limb sounder Aura/MLS. The study covers the stratosphere and middle mesosphere from 50 to 0.05 hPa (from 21 to 70 km) and extends over the period from July 2009 to November 2016, which results in more than 3500 coincident profiles available for the comparison. GROMOS and Aura/MLS profiles agree within 3 % for the altitude range from 25 to 55 km, with standard deviations of the mean relative differences around 5 % from 30 to 40 km and tending to 10 % towards the lower and upper stratosphere. Above the stratosphere, the mean relative differences and its standard deviations are increasing with altitude up to 50 % at 70 km. In addition, we have observed the annual variation of nighttime ozone in the middle mesosphere, at 0.05 hPa (70 km), characterised by the enhancement of ozone during wintertime for both ground-based and space-based measurements. This behaviour is explained by the middle mesospheric maximum of ozone (MMM). On the other hand, the amplitude of the diurnal variation, night-to-day ratio (NDR), is not as strong as the observed one at higher latitudes, nevertheless we observe the winter anomaly of the night-to-day ratio.

Causes of interannual variability over the southern hemispheric tropospheric ozone maximum

We examine the relative contribution of processes controlling the interannual variability (IAV) of tropospheric ozone over four sub-regions of the southern hemispheric tropospheric ozone maximum (SHTOM) over a 20-year period. Our study is based on hindcast simulations from the National Aeronautics and Space Administration Global Modeling Initiative chemistry transport model (NASA GMI-CTM) of tropospheric and stratospheric chemistry, driven by assimilated Modern Era Retrospective Analysis for Research and Applications (MERRA) meteorological fields. Our analysis shows that over SHTOM region, the IAV of the stratospheric contribution is the most important factor driving the IAV of upper tropospheric ozone (270 hPa), where ozone has a strong radiative effect. Over the South Atlantic region, the contribution from surface emissions to the IAV of ozone exceeds that from stratospheric input at and below 430 hPa. Over the South Indian Ocean, the IAV of stratospheric ozone makes the largest contribution to the IAV of ozone with little or no influence from surface emissions at 270 and 430 hPa in austral winter. Over the tropical South Atlantic region, the contribution from IAV of stratospheric input dominates in austral winter at 270 hPa and drops to less than half but is still significant at 430 hPa. Emission contributions are not significant at these two levels. The IAV of lightning over this region also contributes to the IAV of ozone in September and December. Over the tropical southeastern Pacific, the contribution of the IAV of stratospheric input is significant at 270 and 430 hPa in austral winter, and emissions have little influence.

On instrumental errors and related correction strategies of ozonesondes: possible effect on calculated ozone trends for the nearby sites Uccle and De Bilt

The ozonesonde stations at Uccle (Belgium) and De Bilt (the Netherlands) are separated by only 175 km but use different ozonesonde types (or different manufacturers for the same electrochemical concentration cell (ECC) type), operating procedures, and correction strategies. As such, these stations form a unique test bed for the Ozonesonde Data Quality Assessment (O3S-DQA) activity, which aims at providing a revised, homogeneous, consistent dataset with an altitude-dependent estimated uncertainty for each revised profile. For the ECC ozonesondes at Uccle mean relative uncertainties in the 4–6 % range are obtained. To study the impact of the corrections on the ozone profiles and trends, we compared the Uccle and De Bilt average ozone profiles and vertical ozone trends, calculated from the operational corrections at both stations and the O3S-DQA corrected profiles. In the common ECC 1997–2014 period, the O3S-DQA corrections effectively reduce the differences between the Uccle and De Bilt ozone partial pressure values with respect to the operational corrections only for the stratospheric layers below the ozone maximum. The upper-stratospheric ozone measurements at both sites are substantially different, regardless of the correction methodology used. The origin of this difference is not clear. The discrepancies in the tropospheric ozone concentrations between both sites can be ascribed to the problematic background measurement and correction at De Bilt, especially in the period before November 1998. The Uccle operational correction method, applicable to both ozonesonde types used, diminishes the relative stratospheric ozone differences of the Brewer–Mast sondes in the 1993–1996 period with De Bilt to less than 5 % and to less than 6 % in the free troposphere for the De Bilt operational corrections. Despite their large impact on the average ozone profiles, the different (sensible) correction strategies do not change the ozone trends significantly, usually only within their statistical uncertainty due to atmospheric noise. The O3S-DQA corrections bring the Uccle and De Bilt ozone trend estimates for 1997–2014 closer to each other in the lower stratosphere and lower troposphere. Throughout the whole vertical profile, these trend estimates are, however, not significantly different from each other, and only in the troposphere significantly positive. For the entire Uccle observation period (1969–2014), the operational corrections lead to height-independent and consistent ozone trends for both the troposphere and the stratosphere, with rates of +2 to +3 % decade−1 and −1 to −2 % decade−1, respectively.