Quality assessment of the Ozone_cci Climate Research Data Package (release 2017) – Part 2: Ground-based validation of nadir ozone profile data products

Atmospheric ozone plays a key role in air quality and the radiation budget of the Earth, both directly and through its chemical influence on other trace gases. Assessments of the atmospheric ozone distribution and associated climate change therefore demand accurate vertically resolved ozone observations with both stratospheric and tropospheric sensitivity, on both global and regional scales, and both in the long term and at shorter timescales. Such observations have been acquired by two series of European nadir-viewing ozone profilers, namely the scattered-light UV–visible spectrometers of the GOME family, launched regularly since 1995 (GOME, SCIAMACHY, OMI, GOME-2A/B, TROPOMI, and the upcoming Sentinel-5 series), and the thermal infrared emission sounders of the IASI type, launched regularly since 2006 (IASI on Metop platforms and the upcoming IASI-NG on Metop-SG). In particular, several Level-2 retrieved, Level-3 monthly gridded, and Level-4 assimilated nadir ozone profile data products have been improved and harmonized in the context of the ozone project of the European Space Agency's Climate Change Initiative (ESA Ozone_cci). To verify their fitness for purpose, these ozone datasets must undergo a comprehensive quality assessment (QA), including (a) detailed identification of their geographical, vertical, and temporal domains of validity; (b) quantification of their potential bias, noise, and drift and their dependences on major influence quantities; and (c) assessment of the mutual consistency of data from different sounders. For this purpose we have applied to the Ozone_cci Climate Research Data Package (CRDP) released in 2017 the versatile QA and validation system Multi-TASTE, which has been developed in the context of several heritage projects (ESA's Multi-TASTE, EUMETSAT's O3M-SAF, and the European Commission's FP6 GEOmon and FP7 QA4ECV). This work, as the second in a series of four Ozone_cci validation papers, reports for the first time on data content studies, information content studies and ground-based validation for both the GOME- and IASI-type climate data records combined. The ground-based reference measurements have been provided by the Network for the Detection of Atmospheric Composition Change (NDACC), NASA's Southern Hemisphere Additional Ozonesonde programme (SHADOZ), and other ozonesonde and lidar stations contributing to the World Meteorological Organisation's Global Atmosphere Watch (WMO GAW). The nadir ozone profile CRDP quality assessment reveals that all nadir ozone profile products under study fulfil the GCOS user requirements in terms of observation frequency and horizontal and vertical resolution. Yet all L2 observations also show sensitivity outliers in the UTLS and are strongly correlated vertically due to substantial averaging kernel fluctuations that extend far beyond the kernel's 15 km FWHM. The CRDP typically does not comply with the GCOS user requirements in terms of total uncertainty and decadal drift, except for the UV–visible L4 dataset. The drift values of the L2 GOME and OMI, the L3 IASI, and the L4 assimilated products are found to be overall insignificant, however, and applying appropriate altitude-dependent bias and drift corrections make the data fit for climate and atmospheric composition monitoring and modelling purposes. Dependence of the Ozone_cci data quality on major influence quantities – resulting in data screening suggestions to users – and perspectives for the Copernicus Sentinel missions are additionally discussed

Comprehensive quality assessment of GOME- and IASI-type multi-mission tropospheric ozone data records

International audienceTropospheric ozone plays a key role in air quality and has a significant impact on the radiation budget of the Earth, both directly and through its chemical influence on other trace gases. Assessments of atmospheric composition change and of associated climate change therefore demand accurate observations of the tropospheric ozone, both on the global and regional scales and both in the longer and shorter term. Such observations have been provided by two series of European nadir-viewing ozone profilers, namely the scattered-light UV-visible spectrometers of the GOME type, launched regularly since 1995 (GOME, SCIAMACHY, OMI, GOME-2 on MetOp-A/B/C, and the upcoming S-5p TROPOMI and Sentinel-5 missions), and the thermal infrared emission sounders of the IASI type, launched regularly since 2006 (IASI on MetOp platforms and IASI-NG on MetOp-SG). In particular, several tro- pospheric ozone data products have been improved and harmonised in the context of the European Space Agency’s Climate Change Initiative (ESA CCI) on ozone (www.esa-ozone-cci.org). To verify their fitness-for-purpose, those tropospheric ozone datasets must undergo a comprehensive quality assessment (QA), including (a) detailed iden- tification of their geographical, vertical and temporal domains of validity, (b) quantification of their potential bias, noise and drift and their dependences on influence quantities, and (c) assessment of the mutual consistency of data from different sounders. For this purpose we have applied to the aforementioned Ozone CCI datasets a versatile QA/validation system developed over years in the context of ESA’s Multi-TASTE and CCI projects, EUMETSAT’s O3M-SAF, and the European Commission’s GEOmon and QA4ECV. For both GOME- and IASI-type climate data records we report on data content studies, information content studies, and comparisons with co-located reference observations from the well established NDACC, SHADOZ, and GAW ozonesonde networks. Dependence of the tropospheric ozone data quality on major influence quantities and perspectives for the future Sentinel missions are discussed

Quality assessment of the Ozone_cci Climate Research Data Package (release 2017) – Part 2: Ground-based validation of nadir ozone profile data products

International audienceAtmospheric ozone plays a key role in air quality and the radiation budget of the Earth, both directly and through its chemical influence on other trace gases. Assessments of the atmospheric ozone distribution and associated climate change therefore demand accurate vertically resolved ozone observations with both stratospheric and tropospheric sensitivity, on both global and regional scales, and both in the long term and at shorter timescales. Such observations have been acquired by two series of European nadir-viewing ozone profilers, namely the scattered-light UV–visible spectrometers of the GOME family, launched regularly since 1995 (GOME, SCIAMACHY, OMI, GOME-2A/B, TROPOMI, and the upcoming Sentinel-5 series), and the thermal infrared emission sounders of the IASI type, launched regularly since 2006 (IASI on Metop platforms and the upcoming IASI-NG on Metop-SG). In particular, several Level-2 retrieved, Level-3 monthly gridded, and Level-4 assimilated nadir ozone profile data products have been improved and harmonized in the context of the ozone project of the European Space Agency's Climate Change Initiative (ESA Ozone_cci). To verify their fitness for purpose, these ozone datasets must undergo a comprehensive quality assessment (QA), including (a) detailed identification of their geographical, vertical, and temporal domains of validity; (b) quantification of their potential bias, noise, and drift and their dependences on major influence quantities; and (c) assessment of the mutual consistency of data from different sounders. For this purpose we have applied to the Ozone_cci Climate Research Data Package (CRDP) released in 2017 the versatile QA and validation system Multi-TASTE, which has been developed in the context of several heritage projects (ESA's Multi-TASTE, EUMETSAT's O3M-SAF, and the European Commission's FP6 GEOmon and FP7 QA4ECV). This work, as the second in a series of four Ozone_cci validation papers, reports for the first time on data content studies, information content studies and ground-based validation for both the GOME- and IASI-type climate data records combined. The ground-based reference measurements have been provided by the Network for the Detection of Atmospheric Composition Change (NDACC), NASA's Southern Hemisphere Additional Ozonesonde programme (SHADOZ), and other ozonesonde and lidar stations contributing to the World Meteorological Organisation's Global Atmosphere Watch (WMO GAW). The nadir ozone profile CRDP quality assessment reveals that all nadir ozone profile products under study fulfil the GCOS user requirements in terms of observation frequency and horizontal and vertical resolution. Yet all L2 observations also show sensitivity outliers in the UTLS and are strongly correlated vertically due to substantial averaging kernel fluctuations that extend far beyond the kernel's 15km FWHM. The CRDP typically does not comply with the GCOS user requirements in terms of total uncertainty and decadal drift, except for the UV–visible L4 dataset. The drift values of the L2 GOME and OMI, the L3 IASI, and the L4 assimilated products are found to be overall insignificant, however, and applying appropriate altitude-dependent bias and drift corrections make the data fit for climate and atmospheric composition monitoring and modelling purposes. Dependence of the Ozone_cci data quality on major influence quantities – resulting in data screening suggestions to users – and perspectives for the Copernicus Sentinel missions are additionally discussed

Overview of the main achievements of the Ozone Climate Change Initiative Project

International audienceAtmospheric ozone is an Essential Climate Variable which impacts the radiation budget of the Earth, interacts with atmospheric dynamics and climate, and influences chemically other radiatively active species. As part of the Ozone Climate Change Initiative (Ozone_cci) project, a large number of ozone data sets have been generated from a full suite of atmospheric chemistry satellite missions. Following a first phase of 3 years during which new and improved algorithms and data products have been demonstrated and assessed against well-defined user requirements, the ongoing second phase of the Ozone_cci concentrates on extending and further improving these data sets with the ambition to realize the full potential of the existing archive of satellite ozone sensors. We present an overview of the main realizations of the project. This covers long-series of consistent ozone columns and profiles derived from nadir UV sensors and the thermal infrared IASI instrument. Also addressed is the generation of a large scale coherent data base of vertically resolved ozone measurements derived from a full suite of limb and occultation sensors, optimised for accuracy in a broad range of altitudes extending from the UT/LS to the mesosphere