Homogenization of the long-term global ozonesonde records

Póster presentado en: WMO Technical Conference on Meteorological and Environmental Instruments and Methods of Observation celebrada del 10 al 13 de octubre de 2022 en París

Time series analysis of Arctic tropospheric ozone as short-lived climate force

Ozone soundings from 9 Nordic stations with rather different data coverage have been homogenized followed by an interpolation to standard tropospheric pressure levels. A Bayesian model was applied which included a low-frequency variability, an annual cycle with harmonics, the possibility for variability in seasonal amplitude and phasing, and noise. Regarding the low-frequency variability it was found that only Scoresbysund, Ny Aalesund and Sodankyla showed statistical significant changes with a maximum near 2007 followed by a decrease. We hypothesize that this decrease could be explained by an observed decrease in nitrogen oxide in Europe

Trends and annual cycles in soundings of Arctic tropospheric ozone

Ozone soundings from nine Nordic stations have been homogenized and interpolated to standard pressure levels. The different stations have very different data coverage; the longest period with data is from the end of the 1980s to 2014. At each pressure level the homogenized ozone time series have been analysed with a model that includes both low-frequency variability in the form of a polynomial, an annual cycle with harmonics, the possibility for low-frequency variability in the annual amplitude and phasing, and either white noise or noise given by a first-order autoregressive process. The fitting of the parameters is performed with a Bayesian approach not only giving the mean values but also confidence intervals. The results show that all stations agree on a well-defined annual cycle in the free troposphere with a relatively confined maximum in the early summer. Regarding the low-frequency variability, it is found that Scoresbysund, Ny Ålesund, Sodankylä, Eureka, and Ørland show similar, significant signals with a maximum near 2005 followed by a decrease. This change is characteristic for all pressure levels in the free troposphere. A significant change in the annual cycle was found for Ny Ålesund, Scoresbysund, and Sodankylä. The changes at these stations are in agreement with the interpretation that the early summer maximum is appearing earlier in the year. The results are shown to be robust to the different settings of the model parameters such as the order of the polynomial, number of harmonics in the annual cycle, and the type of noise

Air Quality in the Nordic Countries and Climate Changes in the Arctic : LINKA

The report use ozone measurement data retrieved in the Arctic with balloon borne ozone sondes for the last 20-30 years. Four stations with the best data series have been selected. Using a Monte Carlo method the yearly period is subtracted from the data and the remains, the anomalies, are correlated towards the area of the Polar Front, the temperature rise of the Nortern Hemisphere and the North Atlantic Oscillation (NAO) and towards one another. It was found that the NAO correlates negatively with ozone anomalies for all four stations albeit the correlations are weak. Besides, the polar front area correlates weakly positive with the ozone anomalies for three out of the four stations. These results, together with the observation that the ozone-anomalies have a brief decorrelation time, indicate that most of the variability in the anomalies should be found in local conditions

Total ozone loss during the 2017/18 Arctic winter and comparison to previous years

International audienceThe amplitude of ozone depletion in the Arctic is monitored every year since 1994 by comparison between total ozone measurements of eight SAOZ / NDACC UV-Vis spectrometers deployed in the Arctic and 3-D chemical transport model simulations in which ozone is considered as a passive tracer.The method allows determining the evolution of the daily rate of the ozone destruction and the amplitude of the cumulative loss at the end of the winter. The amplitude of the destruction varies between 0-10% in relatively warm and short vortex duration years to 25-39% in colder and longer ones.However, as shown by the unprecedented depletion of 39% in 2010/11, the loss is not only dependent on the extension of the vortex in spring, but also on its strength limiting its re-noxification by import of nitrogen oxide species from the outside, as reported by the total NO2 columns measured by the SAOZ instruments.Shown in this presentation will be the evolution of ozone loss and re-noxification in the Arctic during the winter 2017/18 compared to that of previous winters.Compared to observed SAOZ O3 loss, REPROBUS and SLIMCAT CTM simulations are showing similar losses, however the agreement may vary from one year to the other, depending on the assumptions of vortex strength and isolation. The comparison between ozone loss amplitudes and ozone loss rates, seen each year since 1994 by SAOZ and the two CTM simulations will be followed by a discussion of possible causes in their variable amplitude

Total ozone loss during the 2021/22 Arctic winter and comparison to previous years

International audienceThe amplitude and rate of ozone depletion in the Arctic is monitored every year since 1994 by comparison between SAOZ UV-Vis ground-based network from NDACC and Multi-Sensor Reanalysis 2 (MSR-2) total ozone measurements over 8 stations in the Arctic and 3-D chemical transport model simulations in which ozone is considered as a passive tracer. The passive ozone method allows determining the cumulative loss at the end of the winter. The amplitude of the destruction varies between 0-10% in relatively warm and short vortex duration years to 25-38% in colder and longer ones, which the record winters estimated in 2010/2011 and 2019/2020.In this study, the interannual variability of 10-days average rate of 2021/2022 winter will be analyzed and compared to previous years. In addition, SAOZ NO2 data will be used to evaluate re- noxification in the Arctic. The long-term ozone loss series estimated from measurements will be compared to REPROBUS and SLIMCAT CTM simulations. Relationship with illuminated Polar Stratospheric Clouds will be also presented

Trends in polar ozone loss since 1989: potential sign of recovery in the Arctic ozone column

International audienceOzone depletion over the polar regions is monitored each year by satellite- and ground-based instru- ments. In this study, the vortex-averaged ozone loss over the last 3 decades is evaluated for both polar regions using the passive ozone tracer of the chemical transport model TOMCAT/SLIMCAT and total ozone observa- tions from Système d’Analyse par Observation Zénithale (SAOZ) ground-based instruments and Multi-Sensor Reanalysis (MSR2). The passive-tracer method allows us to determine the evolution of the daily rate of column ozone destruction and the magnitude of the cumulative column loss at the end of the winter. Three metrics are used in trend analyses that aim to assess the ozone recovery rate over both polar regions: (1) the maximum ozone loss at the end of the winter, (2) the onset day of ozone loss at a specific threshold, and (3) the ozone loss residuals computed from the differences between annual ozone loss and ozone loss values regressed with respect to sunlit volume of polar stratospheric clouds (VPSCs). This latter metric is based on linear and parabolic regressions for ozone loss in the Northern Hemisphere and Southern Hemisphere, respectively. In the Antarctic, metrics 1 and 3 yield trends of −2.3 % and −2.2 % per decade for the 2000–2021 period, significant at 1 and 2 standard deviations (σ ), respectively. For metric 2, various thresholds were considered at the total ozone loss values of 20%, 25%, 30%, 35%, and 40%, all of them showing a time delay as a function of year in terms of when the threshold is reached. The trends are significant at the 2σ level and vary from 3.5 to 4.2 d per decade between the various thresholds. In the Arctic, metric 1 exhibits large interannual variability, and no significant trend is detected; this result is highly influenced by the record ozone losses in 2011 and 2020. Metric 2 is not applied in the Northern Hemisphere due to the difficulty in finding a threshold value in enough of the winters. Metric 3 pro- vides a negative trend in Arctic ozone loss residuals with respect to the sunlit VPSC fit of −2.00 ± 0.97 (1σ ) % per decade, with limited significance at the 2σ level. With such a metric, a potential quantitative detection of ozone recovery in the Arctic springtime lower stratosphere can be made