A process-oriented evaluation of CAMS reanalysis ozone during tropopause folds over Europe for the period 2003–2018

Abstract. Tropopause folds are the key process underlying stratosphere-to-troposphere transport (STT) of ozone, and thus they affect tropospheric ozone levels variability. In present study we perform a process-oriented evaluation Copernicus Atmosphere Monitoring Service (CAMS) reanalysis (CAMSRA) O3 during folding events over Europe for time period from 2003 to 2018. A 3-D labeling algorithm is applied detect tropopause in CAMSRA, while ozonesonde data WOUDC (World Ozone Ultraviolet Radiation Data Centre) aircraft measurements IAGOS (In-service Aircraft Global Observing System) used CAMSRA evaluation. The profiles observed concentrations indicate that reproduces increases troposphere examined events. Nevertheless, at most sites, overestimates concentrations, mostly upper portion increases, with median fractional gross error (FGE) among sites >0.2 above 400 hPa. use control run without assimilation reveals aforementioned overestimation arises implementation. Overall, although assists follow enhancements STT events, it introduces biases resulting no clear quantitative improvement compared assimilation. Less biased assimilated products, finer vertical resolution troposphere, addition higher IFS (Integrated Forecasting resolution, expected provide better representation variability folds.