A Post‐2013 Dropoff in Total Ozone at a Third of Global Ozonesonde Stations: Electrochemical Concentration Cell Instrument Artifacts?

An international effort to improve ozonesonde data quality and to reevaluate historical records has made significant improvements in the accuracy of global network data. However, between 2014 and 2016, ozonesonde total column ozone (TCO; O3) at 14 of 37 regularly reporting stations exhibited a sudden dropoff relative to satellite measurements. The ozonesonde TCO drop is 3–7% compared to satellite and ground‐based TCO, and 5–10% or more compared to satellite stratospheric O3 profiles, compromising the use of recent data for trends, although they remain reliable for other uses. Hardware changes in the ozonesonde instrument are likely a major factor in the O3 dropoff, but no single property of the ozonesonde explains the findings. The bias remains in recent data. Research to understand the dropoff is in progress; this letter is intended as a caution to users of the data. Our findings underscore the importance of regular ozonesonde data evaluation

A Post‐2013 Dropoff in Total Ozone at a Third of Global Ozonesonde Stations: Electrochemical Concentration Cell Instrument Artifacts?

An international effort to improve ozonesonde data quality and to reevaluate historical records has made significant improvements in the accuracy of global network data. However, between 2014 and 2016, ozonesonde total column ozone (TCO; O3) at 14 of 37 regularly reporting stations exhibited a sudden dropoff relative to satellite measurements. The ozonesonde TCO drop is 3–7% compared to satellite and ground‐based TCO, and 5–10% or more compared to satellite stratospheric O3 profiles, compromising the use of recent data for trends, although they remain reliable for other uses. Hardware changes in the ozonesonde instrument are likely a major factor in the O3 dropoff, but no single property of the ozonesonde explains the findings. The bias remains in recent data. Research to understand the dropoff is in progress; this letter is intended as a caution to users of the data. Our findings underscore the importance of regular ozonesonde data evaluation

Five years of Sentinel-5p TROPOMI operational ozone profiling and geophysical validation using ozonesonde and lidar ground-based networks

International audienceThe Sentinel-5 Precursor (S5P) satellite operated by the European Space Agency (ESA) carries the TROPOspheric Monitoring Instrument (TROPOMI) on a Sun-synchronous low-Earth orbit since October 13, 2017. The S5P mission has acquired more than five years of TROPOMI nadir ozone profile data retrieved from the Level-0-to-1B processor version 2.0 and the Level-1B-to-2 Optimal Estimation based processor version 2.4.0. The latter is described in detail in this work, followed by the geophysical validation of the resulting ozone profiles for the period May 2018 to April 2023. Comparison of TROPOMI 5 ozone profile data to co-located ozonesonde and lidar measurements used as references, concludes to a median agreement better than 5 to 10 % in the troposphere. The bias goes up to-15 % in the upper stratosphere (35-45 km) where it can exhibit vertical oscillations. The comparisons show a dispersion of about 30 % in the troposphere and 10 to 20 % in the upper troposphere to lower stratosphere (UTLS) and in the middle stratosphere, which is close to mission requirements. Chi-square tests of the observed differences confirm on average the validity of the ex-ante (prognostic) satellite and ground-based data 10 uncertainty estimates in the middle stratosphere, above about 20 km. Around the tropopause and below, the mean chi-square

5 years of Sentinel-5P TROPOMI operational ozone profiling and geophysical validation using ozonesonde and lidar ground-based networks

International audienceThe Sentinel-5 Precursor (S5P) satellite operated by the European Space Agency (ESA) carries the TROPOspheric Monitoring Instrument (TROPOMI) on a Sun-synchronous low-Earth orbit since October 13, 2017. The S5P mission has acquired more than five years of TROPOMI nadir ozone profile data retrieved from the Level-0-to-1B processor version 2.0 and the Level-1B-to-2 Optimal Estimation based processor version 2.4.0. The latter is described in detail in this work, followed by the geophysical validation of the resulting ozone profiles for the period May 2018 to April 2023. Comparison of TROPOMI 5 ozone profile data to co-located ozonesonde and lidar measurements used as references, concludes to a median agreement better than 5 to 10 % in the troposphere. The bias goes up to-15 % in the upper stratosphere (35-45 km) where it can exhibit vertical oscillations. The comparisons show a dispersion of about 30 % in the troposphere and 10 to 20 % in the upper troposphere to lower stratosphere (UTLS) and in the middle stratosphere, which is close to mission requirements. Chi-square tests of the observed differences confirm on average the validity of the ex-ante (prognostic) satellite and ground-based data 10 uncertainty estimates in the middle stratosphere, above about 20 km. Around the tropopause and below, the mean chi-square

SHADOZ (Southern Hemisphere Additional Ozonesondes) Ozone Climatology. 4. Tropospheric and Lower Stratospheric Profiles (2005-2009) with Comparisons to OMI Total Ozone

International audienceWe present a regional and seasonal climatology of SHADOZ ozone profiles in the troposphere and tropical tropopause layer (TTL) based on measurements taken during the first five years of Aura, 2005-2009, when new stations joined the network at Hanoi, Vietnam; Hilo, Hawaii; Alajuela/Heredia, Costa Rica; Cotonou, Benin. In all, 15 stations operated during that period. A west-to-east progression of decreasing convective influence and increasing pollution leads to distinct tropospheric ozone profiles in three regions: (1) western Pacific/eastern Indian Ocean; (2) equatorial Americas (San Cristóbal, Alajuela, Paramaribo); (3) Atlantic and Africa. Comparisons in total ozone column from soundings, the Ozone Monitoring Instrument (OMI, on Aura, 2004-) satellite and ground-based instrumentation are presented. Most stations show better agreement with OMI than they did for EP/TOMS comparisons (1998-2004; Earth-Probe/Total Ozone Mapping Spectrometer), partly due to a revised above-burst ozone climatology. Possible station biases in the stratospheric segment of the ozone measurement noted in the first 7 years of SHADOZ ozone profiles are re-examined. High stratospheric bias observed during the TOMS period appears to persist at one station. Comparisons of SHADOZ tropospheric ozone and the daily Trajectory-enhanced Tropospheric Ozone Residual (TTOR) product (based on OMI/MLS) show that the satellite-derived column amount averages 25% low. Correlations between TTOR and the SHADOZ sondes are quite good (typical r2 = 0.5-0.8), however, which may account for why some published residual-based OMI products capture tropospheric interannual variability fairly realistically. On the other hand, no clear explanations emerge for why TTOR-sonde discrepancies vary over a wide range at most SHADOZ sites