The effect of climate change on the upper stratospheric ozone depletion from Umkehr measurements over Antarctica

第１回極域科学シンポジウム「極域大気圏を通して探る地球規模環境変動」ポスター発

Ozone recovery in the upper stratosphere from Umkehr measurement over Syowa, Antarctica

第3回極域科学シンポジウム/第35回極域気水圏シンポジウム 11月30日（金） 国立国語研究所 ２階ロビ

Long term changes in the upper stratospheric ozone at Syowa, Antarctica

第2回極域科学シンポジウム/第35回極域宙空圏シンポジウム 11月15日（火） 国立極地研究所 2階大会議

The Network for the Detection of Atmospheric Composition Change (NDACC): history, status and perspectives

The Network for the Detection of Atmospheric Composition Change (NDACC) is an international global network of more than 90 stations making high-quality measurements of atmospheric composition that began official operations in 1991 after 5 years of planning. Apart from sonde measurements, all measurements in the network are performed by ground-based remote-sensing techniques. Originally named the Network for the Detection of Stratospheric Change (NDSC), the name of the network was changed to NDACC in 2005 to better reflect the expanded scope of its measurements. The primary goal of NDACC is to establish long-term databases for detecting changes and trends in the chemical and physical state of the atmosphere (mesosphere, stratosphere, and troposphere) and to assess the coupling of such changes with climate and air quality. NDACC's origins, station locations, organizational structure, and data archiving are described. NDACC is structured around categories of ground-based observational techniques (sonde, lidar, microwave radiometers, Fourier-transform infrared, UV-visible DOAS (differential optical absorption spectroscopy)-type, and Dobson–Brewer spectrometers, as well as spectral UV radiometers), timely cross-cutting themes (ozone, water vapour, measurement strategies, cross-network data integration), satellite measurement systems, and theory and analyses. Participation in NDACC requires compliance with strict measurement and data protocols to ensure that the network data are of high and consistent quality. To widen its scope, NDACC has established formal collaborative agreements with eight other cooperating networks and Global Atmosphere Watch (GAW). A brief history is provided, major accomplishments of NDACC during its first 25 years of operation are reviewed, and a forward-looking perspective is presented

Updated trends of the stratospheric ozone vertical distribution in the 60 degrees S-60 degrees N latitude range based on the LOTUS regression model

This study presents an updated evaluation of stratospheric ozone profile trends in the 60∘&thinsp;S&ndash;60∘&thinsp;N latitude range over the 2000&ndash;2020 period using an updated version of the Long-term Ozone Trends and Uncertainties in the Stratosphere (LOTUS) regression model that was used to evaluate such trends up to 2016 for the last WMO Ozone Assessment (2018). In addition to the derivation of detailed trends as a function of latitude and vertical coordinates, the regressions are performed with the datasets averaged over broad latitude bands, i.e. 60&ndash;35∘&thinsp;S, 20∘&thinsp;S&ndash;20∘&thinsp;N and 35&ndash;60∘&thinsp;N. The same methodology as in the last assessment is applied to combine trends in these broad latitude bands in order to compare the results with the previous studies. Longitudinally resolved merged satellite records are also considered in order to provide a better comparison with trends retrieved from ground-based records, e.g. lidar, ozonesondes, Umkehr, microwave and Fourier transform infrared (FTIR) spectrometers at selected stations where long-term time series are available. The study includes a comparison with trends derived from the REF-C2 simulations of the Chemistry Climate Model Initiative (CCMI-1). This work confirms past results showing an ozone increase in the upper stratosphere, which is now significant in the three broad latitude bands. The increase is largest in the Northern and Southern Hemisphere midlatitudes, with &sim;2.2&thinsp;&plusmn;&thinsp;0.7&thinsp;% per decade at &sim;2.1&thinsp;hPa and &sim;2.1&thinsp;&plusmn;&thinsp;0.6&thinsp;% per decade at &sim;3.2&thinsp;hPa respectively compared to &sim;1.6&thinsp;&plusmn;&thinsp;0.6&thinsp;% per decade at &sim;2.6&thinsp;hPa in the tropics. New trend signals have emerged from the records, such as a significant decrease in ozone in the tropics around 35&thinsp;hPa and a non-significant increase in ozone in the southern midlatitudes at about 20&thinsp;hPa. Non-significant negative ozone trends are derived in the lowermost stratosphere, with the most pronounced trends in the tropics. While a very good agreement is obtained between trends from merged satellite records and the CCMI-1 REF-C2 simulation in the upper stratosphere, observed negative trends in the lower stratosphere are not reproduced by models at southern and, in particular, at northern midlatitudes, where models report an ozone increase. However, the lower-stratospheric trend uncertainties are quite large, for both measured and modelled trends. Finally, 2000&ndash;2020 stratospheric ozone trends derived from the ground-based and longitudinally resolved satellite records are in reasonable agreement over the European Alpine and tropical regions, while at the Lauder station in the Southern Hemisphere midlatitudes they show some differences. &nbsp;</p

What controls long-term Ozone changes other than Ozone-Depleting Substances in the Antarctic stratosphere?

In the upper stratosphere the inter-annual variability of ozone is mostly controlled by chemical reactions and is strongly influenced by the anthropogenic ozone-depleting substances (ODS). While at middle latitudes the ODS reached the maximum in the stratosphere by the end of 1990s, at high latitudes the turning in the growth rate of the ODS has been delayed by several years. Analysis of Umkehr observations helps to understand the influence of the ODS on ozone in the middle and upper stratosphere. We investigated the long-term trend in the upper stratospheric ozone over the Antarctic using re-processed Umkehr data at Syowa station (69.0 S, 39.5 E). The long-term variability and trend observed in Umkehr ozone profile data is in good agreement with the station’s overpass subset of the SBUV V8.6 Merged Ozone Dataset. The long-term trend is affected by the changes in the polar vortex position and its persistence relative to the geophysical location of Syowa station. We have found a high correlation between the Equivalent Latitude (EqLat) at 850K (10 hPa or 32 km) and stratospheric ozone. The Southern Hemisphere Annular Mode (SAM) is also considered as one of the explanatory parameters in our analysis of ozone variability over Syowa. High correlation is found between stratospheric ozone and SAM during high solar activity years (HS, 1978-1982, 1988-1992, and 1998-2002). The largest variability in the Antarctic stratosphere related to the SAM signal is observed from September to December. Since the SAM and upper stratospheric ozone are both affected by planetary wave propagation, their correlation reflects their response to the same mechanism, especially during HS.In this presentation, we describe attribution of ozone variability to the proxies and discuss differences in factors that affect upper, middle and lower stratospheric ozone over Syowa.第4回極域科学シンポジウム個別セッション：[OM] 気水圏11月14日（木） 統計数理研究所 ３階セミナー室１（D305

Retrieving vertical ozone profiles from measurements of global spectral irradiance

A new method is presented to determine vertical ozone profiles from measurements of spectral global (direct Sun plus upper hemisphere) irradiance in the ultraviolet. The method is similar to the widely used Umkehr technique, which inverts measurements of zenith sky radiance. The procedure was applied to measurements of a high-resolution spectroradiometer installed near the centre of the Greenland ice sheet. Retrieved profiles were validated with balloonsonde observations and ozone profiles from the space-borne Microwave Limb Sounder (MLS). Depending on altitude, the bias between retrieval results presented in this paper and MLS observations ranges between -5 and + 3 %. The magnitude of this bias is comparable, if not smaller, to values reported in the literature for the standard Dobson Umkehr method. Total ozone columns (TOCs) calculated from the retrieved profiles agree to within 0.7 +/- 2.0% (+/- 1 sigma) with TOCs measured by the Ozone Monitoring Instrument on board the Aura satellite. The new method is called the "Global-Umkehr" method

Variations in the vertical profile of ozone at four high-latitude Arctic sites from 2005 to 2017

Understanding variations in atmospheric ozone in the Arctic is difficult because there are only a few long-term records of vertical ozone profiles in this region. We present 12 years of ozone profiles from February 2005 to February 2017 at four sites: Summit Station, Greenland; Ny-Alesund, Svalbard, Norway; and Alert and Eureka, Nunavut, Canada. These profiles are created by combining ozonesonde measurements with ozone profile retrievals using data from the Microwave Limb Sounder (MLS). This combination creates a high-quality dataset with low uncertainty values by relying on in situ measurements of the maximum altitude of the ozonesondes (similar to 30 km) and satellite retrievals in the upper atmosphere (up to 60 km). For each station, the total column ozone (TCO) and the partial column ozone (PCO) in four atmospheric layers (troposphere to upper stratosphere) are analyzed. Overall, the seasonal cycles are similar at these sites. However, the TCO over Ny-Alesund starts to decline 2 months later than at the other sites. In summer, the PCO in the upper stratosphere over Summit Station is slightly higher than at the other sites and exhibits a higher standard deviation. The decrease in PCO in the middle and upper stratosphere during fall is also lower over Summit Station. The maximum value of the lower- and middle-stratospheric PCO is reached earlier in the year over Eureka. Trend analysis over the 12-year period shows significant trends in most of the layers over Summit and Ny-Alesund during summer and fall. To understand deseasonalized ozone variations, we identify the most important dynamical drivers of Arctic ozone at each level. These drivers are chosen based on mutual selected proxies at the four sites using stepwise multiple regression (SMR) analysis of various dynamical parameters with deseasonalized data. The final regression model is able to explain more than 80 % of the TCO and more than 70 % of the PCO in almost all of the layers. The regression model provides the greatest explanatory value in the middle stratosphere. The important proxies of the deseasonalized ozone time series at the four sites are tropopause pressure (TP) and equivalent latitude (EQL) at 370 K in the troposphere, the quasi-biennial oscillation (QBO) in the troposphere and lower stratosphere, the equivalent latitude at 550 K in the middle and upper stratosphere, and the eddy heat flux (EHF) and volume of polar stratospheric clouds throughout the stratosphere.</p

South Pole Station ozonesondes: variability and trends in the springtime Antarctic ozone hole 1986&ndash;2021

Balloon-borne ozonesondes launched weekly from South Pole station (1986&ndash;2021) measure high vertical resolution profiles of ozone and temperature from surface to 30&ndash;35 km altitude. The launch frequency is increased in late winter before the onset of rapid stratospheric ozone loss in September. Ozone hole metrics show the yearly total column ozone and 14&ndash;21 km column ozone minimum values and September loss rates remain on an upward (less severe) trend since 2001. However, the data series also illustrate interannual variability, especially in the last three years (2019&ndash;2021). Here we show additional details of these three years by comparing minimum ozone profiles and the July&ndash;December 14&ndash;21 km column ozone time series. The 2019 anomalous vortex breakdown showed stratospheric temperatures began warming in early September leading to reduced ozone loss. The minimum total column ozone of 180 Dobson Units (DU) was observed on 24 September. This was followed by two stable and cold polar vortex years in 2020 and 2021 with total column ozone minimums at 104 DU (01 October) and 102 DU (07 October), respectively. These years also showed broad zero ozone (saturation loss) regions within the 14&ndash;21 km layer by the end of September which persisted into October. Validation of the ozonesonde observations is conducted through the ongoing comparison of total column ozone (TCO) measurements with the South Pole ground-based Dobson spectrophotometer. The ozonesondes show a constant positive offset of 2 &plusmn; 3 % (higher) than the Dobson following a thorough evaluation/homogenization of the ozonesonde record in 2018.</p