|Paper title||Quality assessment of ozone Climate Data Records from ESA’s Climate Change Initiative (Ozone_cci+) for the Copernicus Climate Change Service (C3S)|
|Form of presentation||Poster|
Atmospheric ozone is an Essential Climate Variable (ECV) monitored in the framework of the Global Climate Observing System (GCOS), among others due to its impact on the radiation budget of the Earth, its chemical influence on other radiatively active species, and its role in atmospheric dynamics and climate. Its importance in the context of climate change has led ECMWF to set up a dedicated procurement of state-of-the-art ozone Climate Data Records (CDRs) to the Climate Data Store (CDS) of the Copernicus Climate Change Service (C3S), mainly in the form of level-3/4 gridded data products. In support, ESA ensures the round-robin selection, reprocessing, and further improvement of the underlying level-2 ozone data products and their validation, and the development of new and multi-spectral ozone CDRs through its Climate Change Initiative project on ECV ozone (Ozone_cci). In order to assess the fitness-for-purpose of the datasets procured to the Copernicus CDS, processes have been established both within the Ozone_cci (L2 data) and C3S (L3/4 data) projects to monitor ozone CDR quality, check compliance with GCOS requirements and WMO rolling review of requirements (RRR), and regularly report key performance indicators. The ozone datasets typically undergo a harmonized and comprehensive quality assessment, including: (a) verification of their information content and geographical, vertical and temporal representativeness against specifications; (b) quantification of their bias, noise and decadal drift, and their dependence on major influence quantities; and (c) assessment of the mutual consistency of CDRs from different sounders.
This work summarizes the past development and the operational status of the data production and quality assessment of the ozone CDRs procured to the CDS. These CDRs consist of ozone column and vertical profile datasets at level-3 (monthly gridded) and level-4 (assimilated), from several nadir and limb/occultation satellite sounders, retrieval systems, and merging schemes (see details on C3S Climate Data Store at https://cds.climate.copernicus.eu/). The quality assessment of these climate-oriented ozone data records is based on multi-decade time series of correlative measurements collected from monitoring networks contributing to WMO’s Global Atmosphere Watch, such as GO3OS, NDACC, and SHADOZ. Correlative measurements are quality controlled, harmonized, and compared to the various satellite CDRs using BIRA-IASB’s Multi-TASTE versatile validation system, following the latest state-of-the-art protocols and tools. Comparison results document the current quality of the CDRs, which may exhibit cyclic errors, drifts, and other long-term patterns reflecting, e.g., instrumental degradation, residual biases between different instruments and changes in sampling of atmospheric variability and patterns. The total ozone column CDRs, covering up to four decades, are found to be stable with respect to the reference measurements at the 0.1 % per decade level. Similarly, most nadir and limb profile CDRs achieve a level of stability that is consistent with what is expected from instrument specifications.