DORA is a project funded by the Belgian Science Policy Office (BELSPO) and carried out at the Royal Belgian Institute for Space Aeronomy (BIRA-IASB), from 2023 to 2025.
The project is performed in the context of:
- the LOTUS (Long-term Ozone Trends and Uncertainties) initiative within SPARC (Stratosphere-troposphere Processes and their Role in Climate) and
- the TOAR (Tropospheric Ozone Assessment Report) initiative within IGAC (International Global Atmospheric Chemistry).
The DORA (Detection of Ozone Recovery in the Arctic) project focuses on ozone trends in the Arctic, which currently is a region far less explored in LOTUS and TOAR compared to tropical and mid-latitude regions.
Contrary to the Antarctic, where ozone recovery has been observed for about a decade, the detection of positive ozone trends in the Arctic remains challenging due to higher natural variability of ozone in that region. The trends are expected to be small (few percent/decade) which complicates their detection. This project aims to explore if the ozone recovery in the Arctic can be detected using long-term ground-based observations by reducing the uncertainty on the trends.
Objectives:
Reducing the uncertainty on the trends will be obtained through three objectives:
- Select the best quality ground-based time series in Arctic. Ground-based measurements are cross-compared to two satellite data sets (MEGRIDOP and IASI-CDR). This enables the detection of drifted ground-based data sets we further exclude from our study.
- Use a representativeness study based on CAMS re-analysis data to define regions representative of the same ozone variability. This allows the merging of data sets from different instruments and stations, which reduces the noise in the time-series and increases their sampling.
- Annual and seasonal trends are calculated using a multiple linear regression (MLR) technique involving a set of proxies that represent physical processes influencing the natural ozone variability, reducing the remaining variability in the time-series. The MLR also allows the ozone variability associated with each included process to be quantified. The remaining stratospheric ozone trend can then be mostly attributed to the reduction of ODS and quantified.
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