Search

To further verify the ozone profile reliability of satellite remote sensing for the ozone valley over the Tibetan Plateau in the core area of the South Asian high in summer, we validate the ozone products from the microwave limb sounder (MLS) onboard the Aura satellite over the Tibetan plateau using electrochemical concentration cell (ECC) ozonesonde data of 2016 for Ngari, Tibet. The MLS version four ozone profiles have lower standard deviation in the middle stratosphere (38–10 hPa), whereas the ozonesonde profiles have lower standard deviation in the upper troposphere and lower stratosphere region (200–83 hPa). There are statistically significant differences between these two datasets in most of the stratosphere (10–83 hPa). The mean value of MLS ozone is about 0.8–1.5 mPa greater than that of ECC ozone, which corresponds to a relative deviation of 59 ± 24% at 83 hPa, 24 ± 13% at 68 hPa, 20 ± 5% at 56 hPa, 14 ± 4% at 46 hPa and 38 hPa, and 9 ± 4% in the layers between 32 and 10 hPa. However, there is no statistically significant difference between the two datasets in the upper troposphere (100–200 hPa). [ABSTRACT FROM AUTHOR]

In the present study, vertical distribution of ozone observed using ozonesonde measurements obtained during 2010–2014 from a tropical station Gadanki (13.48°E, 79.18°E) is presented with special emphasis on the variability within the atmospheric boundary layer (ABL), in the free troposphere and in the lower stratosphere. In general, a clear semi-annual oscillation in ozone is seen within ABL and free-troposphere with peak during pre- and post-monsoon seasons. Whereas annual oscillation with peak during monsoon season dominates in the lower stratosphere. Interestingly, there is a delay of one month in the peak in the ozone mixing ratio (OMR) in the free troposphere when compared to the ABL during pre-monsoon and these features are quite different compared to other stations in the Indian region. One of the main objectives of the present study is to examine how well the present satellite (MLS and SABER) and re-analysis (ERA-Interim) ozone data sets represent the variability of ozone over the tropical station. In general, MLS and ERA-Interim overestimate the OMR by 97% and 80%, respectively, near the tropical tropopause, in comparison with ozonesonde data. Thus, caution is to be exercised in using these data sets for investigating the stratosphere–troposphere exchange (STE) process. However, all the three data sets show very good agreement with ozonesonde measurements above 22.5 km. ERA-Interim data set is found to agree well in the free troposphere but not in the ABL. Interestingly, the ozone tropopause is found to be more associated with the convective outflow level than cold point tropopause height. Back trajectory analysis reveals that the observed ozone in the troposphere over Gadanki region is mostly transported from the western region and from the higher altitudes. These features are discussed in the light of current understanding of the generation and transport of the ozone in the troposphere. [ABSTRACT FROM AUTHOR]

Using ozonesonde measurements from 2015 to 2018 at the Jang Bogo station located in the southeastern Antarctic region, we evaluate ozone profiles retrieved from the three satellite measurements that are widely used: Ozone Monitoring Instrument (OMI), Microwave Limb Sounder (MLS), and Ozone Mapping Profiler Suite (OMPS) data. For the fair validation, ozonesonde profiles are smoothed using the weighting function of each satellite retrieval algorithm (i.e., convolution process). Compared with limb-viewing MLS and OMPS ozone profiles, the OMI ozone profiles are relatively less qualified: coarser vertical resolution and larger inter-annual variation. Nevertheless, our validation reveals that the quality of all three satellite ozone profiles looks comparable; In general, difference from ozonesonde profile is ∼1 ppm absolutely, and −20 to 30% relatively at maximum. This quantitative range well corresponds to previous work, meaning that our new validation confirms the reliability of satellite ozone profiles in the southeastern Antarctic region where the measurement data for the validation were not enough. Another interesting feature is the role of a priori ozone profile; Nadir-viewing OMI satellite can have qualified ozone profiles by a proper assumption of a priori ozone profile. Since the performance of limb-viewing ozone profiles is better, however, the careful usage of nadir-viewing ozone profile is still required. We think that the simultaneous usage of multiple satellite ozone profiles can contribute to better understanding of Antarctic ozone characteristics. • Ozonesonde data in Jang Bogo site are newly used for the satellite ozone validation. • Limb-viewing MLS and OMPS ozone profiles show similar accuracy. • The quality of nadir-viewing OMI PROFOZ ozone profile is also reliable. • The importance of a priori data is confirmed for the ozone profile retrieval. [ABSTRACT FROM AUTHOR]

Loss of stratospheric ozone has occurred over the last half a century due to catalytic destruction by halogen-containing anthropogenic compounds. Saturated ozone loss events, when the ozone concentrations decreased to less than or equal to 1 mPa (>95% ozone loss), were studied across nine stations in Antarctica using the Microwave Limb Sounder (MLS) instrument onboard the satellite Aura. The satellite observations were corrected using in situ ozonesonde observations to quantify the saturated ozone loss between 2004 and 2020. The analysis shows that at some stations the original MLS observations underestimated the number of loss events by 5–10%, however, at other stations they were overestimated by the same margin. A couple of stations showed a very good match between the original and corrected MLS data. Irrespective of the bias, the number of loss events decreased gradually from 2004 to 2013 suggesting a recovering trend. After 2013, no significant trend is visible, with large variation seen for especially between 2015 and 2019. The interannual variation was strongly coupled to the temperature, highlighting the key role that polar stratospheric clouds play in causing saturated ozone loss. • MLS profiles corrected using ozonesonde profiles show significant differences in the saturated ozone loss at some stations. • A decreasing trend in saturated loss events is observed between 2004 and 13. • The saturated loss events were strongly coupled to temperature, highlighting the role of polar stratospheric clouds. [ABSTRACT FROM AUTHOR]

In situ ozonesonde observations across nine Antarctic stations were used to validate the vertical profiles retrieved by the satellite-based Microwave Limb Sounder (MLS) instrument from 2004 to 2019. Intra-annual variations in the ozone concentration, along with the shape of the vertical profiles are well reproduced by the MLS with differences in the range of ±20%, although seasonally the differences were as high as 60%. The largest differences were also observed during the spring (September-October-November), when largescale ozone depletion takes place over Antarctica, with MLS overestimating concentrations at almost all the stations, except the northernmost stations of Marambio and Dumont d'Urville. This has implications for the estimations of ozone recovery over Antarctica based on MLS. The under-estimation or over-estimation in the MLS data caused differences up to ±1 K day−1 in the estimated heating rate. For the whole dataset, a good correlation (R2 > 0.9, p < 0.001) was seen at all the stations except at Maitri, where the correlation coefficient was lower but still significant (R2 = 0.77, p < 0.001). These results show that although the MLS data match the in-situ observations over longer averaging periods, for individual profiles the discrepancies are much higher and need to be considered when computing the ozone impacts using MLS data. • MLS and in-situ ozonesonde concentrations show significant differences across different stations in Antarctica. • Variability in the vertical distribution was qualitatively well captured by MLS but not quantitatively at all stations. • The differences are not the same across seasons, with most stations showing the largest differences during the springtime. [ABSTRACT FROM AUTHOR]

Ozonesonde data between February 2016 and July 2019 from the Indian Antarctic station 'Bharati' were used for validation of total ozone columns (TCOs) and vertical profiles from satellite-based Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) instruments. Bharati falls in and out of the 'ozone hole' over Antarctica due to the dynamics of the polar vortex, which results in drastic variability. Results show that while both the satellites captured the annual variability in the TCOs, OMI overestimates it by 66.3 DU, i.e. approximately 33% (range: 2.4 to 189.7 DU), while MLS overestimates it by 33.8 DU, i.e. approximately 16% (range: 95.9 to 8.6 DU) compared to the ozonesondes. MLS reproduced the vertical profile variation and peak heights of the ozone layer but overestimated the concentrations compared to the ozonesondes. The overestimation varied with season, with the largest difference during the ozone depletion season in September-October-November (SON: ~40%). MLS and ozonesondes linear fits showed that although the datasets showed good correlation (R2 = 0.97, P < 0.001), there was a significant positive bias in the MLS observations (slope = 1.32 ± 0.38; intercept = 0.55 ± 0.05). This overestimation by MLS also results in an overestimation in the heating rates over Bharati, with the difference peaking in SON at 0.4 ± 0.2 K day−1. • MLS overestimates ozone concentrations at all vertical layers as compared to in-situ ozonesonde observations. • Qualitatively, the vertical distribution and variability at different pressure levels were correctly captured by MLS. • Seasonal variation in the differences between MLS and ozonesondes is observed, with spring showing the largest differences. [ABSTRACT FROM AUTHOR]