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Large-scale meteorological events (e.g. cyclones), referred to as synoptic events, strongly influence weather predictability but still cannot be fully characterised in the Arctic region because of the sparse coverage of measurements. Due to the fact that atmospheric dynamics in the lower stratosphere and troposphere influence the ozone field, one approach to analyse these events further is the use of space-borne measurements of ozone vertical distributions and total columns in addition to conventional parameters such as pressure or wind speed. In this study we investigate the link between cyclones and changes in stratospheric ozone by using a combination of unique measurements during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) ship expedition, ozone profile and total column observations by satellite instruments (OMPS-LP, TROPOMI), and ERA5 reanalysis data. The final goal of the study is to assess whether the satellite ozone data can be used to obtain information about cyclones and provide herewith an additional value in the assimilation by numerical weather prediction models. Three special cases during the MOSAiC expedition were selected and classified for the analysis. They are one "normal" cyclone, where a low surface pressure coincides with a minimum in tropopause height, and two "untypical" cyclones, where this is not observed. The influence of cyclone events on ozone in the upper-troposphere lower-stratosphere (UTLS) region was investigated, using the fact that both are correlated with tropopause height changes. The negative correlation between tropopause height from ERA5 and ozone columns was investigated in the Arctic region for the 3-month period from June to August 2020. This was done using total ozone columns and sub-columns from TROPOMI, OMPS-LP, and MOSAiC ozonesonde data. The greatest influence of tropopause height changes on ozone contour levels occurs at an altitude between 10 and 20 km. Moreover, the lowering of the 250 ppb ozonopause (at about 11 km altitude) below 9 km was used to detect cyclones using OMPS-LP ozone observations. The potential of this approach was demonstrated in two case studies where the boundaries of cyclones could be determined using ozone observations. The results of this study can help improve our understanding of the relationship between cyclones, tropopause height, and ozone in the Arctic and demonstrate the usability of satellite ozone data in addition to the conventional parameters for investigating cyclones in the Arctic. [ABSTRACT FROM AUTHOR]

Due to the unique local air chemistry, the transport history of tropospheric air masses above the remote tropical West Pacific (TWP) is reflected by local ozone (O3) and relative humidity (RH) characteristics. In boreal winter, the TWP is the main global entry point for air masses into the stratosphere and therefore a key region of atmospheric chemistry and dynamics. However, a long-term in situ monitoring of tropospheric O3 to assess the variability of TWP air masses and the respective controlling processes has yet been missing. The aim of our study was to identify air masses with different origins and pathways to the TWP and their seasonality using the new Palau time series (2016–2019) of mostly fortnightly Electrochemical Concentration Cell ozone and radio soundings. Based on monthly statistics of O3 volume mixing ratios and RH we defined a free tropospheric locally-controlled background and analyzed anomalies for both tracers in the 5–10 km altitude range. We found that anomalously high O3 indicates a remote origin, while RH is controlled by a range of dynamical processes resulting in a bimodality in RH anomalies. The Palau time series confirms a year-round presence of low O3 background air masses and a seasonal mid-tropospheric cycle in O3 with a prominent anti-correlation between O3 volume mixing ratios and RH. We assumed five different types of air masses with differing tracer characteristics and origin which we validated by analyzing backward trajectories calculated with the transport module of the Lagrangian chemistry and transport model ATLAS. The main result is a clear separation of origin and pathways for the two most contrasting types of air masses, i.e. ozone-poor and humid versus ozone-rich and dry air. Both, potential vorticity and air mass origin analyses, reveal no indication for stratospheric influence for the ozone-rich dry air masses. Rather, we found indications for O3 production due to biomass burning or anthropogenic pollution at the origins of these air masses and drying due to clear sky subsidence during long-range transport. The seasonal occurrence is tied to the position of the Intertropical Convergence Zone which opens a pathway from potential source regions which are confirmed by the trajectory analysis. We conclude, that dominant ozone-poor and humid air masses are of local or Pacific convective origin and occur year-round, but dominate from August until October. Anomalously dry and ozone-rich air is generated in Tropical Asia and subsequently transported to the TWP via an anti-cyclonic route, mostly from February to April. The areas of origin suggest different sources of ground pollution as a cause for O3 production. We propose large-scale descent within the tropical troposphere and subsequent radiative cooling in connection with the Hadley circulation as responsible for the vertical displacement and dehydration. [ABSTRACT FROM AUTHOR]

Replyingto L. M. Polvani et al. I Nature Commun i I ications i https://doi.org/10.1038/s41467-023-37134-3 (2023) Long-term declines in the thickness of Earth's protective ozone layer have been caused by the decomposition products of organic chlorine and bromine compounds such as chlorofluorocarbons and halons that have been phased out by the Montreal Protocol and its amendments and adjustments. Therefore, we suggest the statement by P22 that "Arctic ozone column in these models are consistent with the observed ozone column over the period 1979-2021" is misleading. Here, we interpret their statement to mean that increased levels of CO SB 2 sb do not amplify the impact of the ODSs on ozone, since we all agree ODSs are the cause of chemical loss of Arctic ozone. 10.1002/jgrd.50316 14 Eyring V. Multi-model assessment of stratospheric ozone return dates and ozone recovery in CCMVal-2 models. [Extracted from the article]

The ozonesonde is a small balloon-borne instrument that is attached to a standard radiosonde to measure profiles of ozone from the surface to 35 km with ∼100-m vertical resolution. Ozonesonde data constitute a mainstay of satellite calibration and are used for climatologies and analysis of trends, especially in the lower stratosphere where satellites are most uncertain. The electrochemical concentration cell (ECC) ozonesonde has been deployed at ∼100 stations worldwide since the 1960s, with changes over time in manufacture and procedures, including details of the cell chemical solution and data processing. As a consequence, there are biases among different stations and discontinuities in profile time series from individual site records. For 22 years the Jülich (Germany) Ozonesonde Intercomparison Experiment (JOSIE) has periodically tested ozonesondes in a simulation chamber designated the World Calibration Centre for Ozonesondes (WCCOS) by WMO. During October–November 2017 a JOSIE campaign evaluated the sondes and procedures used in Southern Hemisphere Additional Ozonesondes (SHADOZ), a 14-station sonde network operating in the tropics and subtropics. A distinctive feature of the 2017 JOSIE was that the tests were conducted by operators from eight SHADOZ stations. Experimental protocols for the SHADOZ sonde configurations, which represent most of those in use today, are described, along with preliminary results. SHADOZ stations that follow WMO-recommended protocols record total ozone within 3% of the JOSIE reference instrument. These results and prior JOSIEs demonstrate that regular testing is essential to maintain best practices in ozonesonde operations and to ensure high-quality data for the satellite and ozone assessment communities. [ABSTRACT FROM AUTHOR]

Reports the results of an approach to calculate chemical ozone destruction rates that allow the comparison between ozone concentrations in specific air parcels at different times. Details of the method; Increase in ozone mixing ratio with altitude in the lower stratosphere.

The West Pacific warm pool has been identified as the major source region for stratospheric air, coinciding with a tropospheric ozone minimum (Rex et al. 2014). The close coupling of ozone concentration and oxidizing capacity of the clean tropical troposphere influences the overall transport of chemical species to the stratosphere. To improve the limited availability of tropospheric ozone profiles from this key region, intensive campaigns and continuous measurements with ECC ozone sondes have been conducted at a new measurement station in Palau (7° N, 135° E) within the scope of the EU-project StratoClim since early 2016. We present the comprehensive instrumental setup of the station and insights from the first three years of balloon-borne measurements regarding seasonality and origin of air masses for specific cases with high/low ozone/water vapor mixing ratios respectively. [ABSTRACT FROM AUTHOR]