A stratospheric prognostic ozone for seamless Earth System Models: performance, impacts and future

• Main Authors: Monge-Sanz, Beatriz M., Bozzo, Alessio, Byrne, Nicholas, Chipperfield, Martyn P., Diamantakis, Michail, Flemming, Johannes, Gray, Lesley J., Hogan, Robin J., Jones, Luke, Magnusson, Linus, Polichtchouk, Inna, Shepherd, Theodore G., Wedi, Nils, Weisheimer, Antje
• Format: Text
• Language: English
• Published: 2021
• Subjects: Antarctic; Arctic; Antarc*; North Atlantic; North Atlantic oscillation
• Online Access: https://doi.org/10.5194/acp-2020-1261; https://acp.copernicus.org/preprints/acp-2020-1261/

We have implemented a new stratospheric ozone model in the European Centre for Medium-Range Weather Forecasts (ECMWF) system, and tested its performance for different timescales, to assess the impact of stratospheric ozone on meteorological fields. We have used the new ozone model to provide prognostic ozone in medium-range and long-range experiments, showing the feasibility of this ozone scheme for a seamless NWP modelling approach. We find that the stratospheric ozone distribution provided by the new scheme in ECMWF forecast experiments is in very good agreement with observations, even for unusual meteorological conditions such as Arctic stratospheric sudden warmings (SSWs) and Antarctic polar vortex events like the vortex split of year 2002. To assess the impact it has on meteorological variables, we have performed experiments in which the prognostic ozone is interactive with radiation. The new scheme provides a realistic ozone field able to improve the description of the stratosphere in the ECMWF system, we find clear reductions of biases in the stratospheric forecast temperature. The seasonality of the Southern Hemisphere polar vortex is also significantly improved when using the new ozone model. In medium-range simulations we also find improvements in high latitude tropospheric winds during the SSW event considered in this study. In long-range simulations the use of the new ozone model leads to an increase in the winter North Atlantic Oscillation (NAO) index correlation, and an increase in the signal to noise ratio over the North Atlantic sector. In our study we show that by improving the description of the stratospheric ozone in the ECMWF system, the stratosphere-tropospheric coupling improves. This highlights the potential benefits of this new ozone model to exploit stratospheric sources of predictability and improve weather predictions over Europe on a range of time scales.