Abstract
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.
Highlights
The new emerging generation of seamless Earth System Models (ESMs) needs to be developed in ways that allow accurate 20 performance in timescales from weather to climate, including seasonal and subseasonal scales
We have implemented the stratospheric ozone model by Monge-Sanz et al (2011) in the European Centre for Medium-Range Weather Forecasts (ECMWF) system, compared its performance to that of the default ozone used by ECMWF, and assessed its impacts on meterological 440 fields at medium-range and seasonal time scales
The new approach is in better agreement with the current scientific knowledge of chemical and physical processes that affect stratospheric ozone (WMO, 2019) than approaches adopted by previous linear ozone models (McLinden et al, 2000; McCormack et al, 2006; Cariolle and Teyssèdre, 2007)
Summary
The new emerging generation of seamless Earth System Models (ESMs) needs to be developed in ways that allow accurate 20 performance in timescales from weather to climate, including seasonal and subseasonal scales. To monitor the effectiveness of the Montreal Protocol, a set of complex atmospheric models was developed to address stratospheric ozone related questions: chemistry-transport models (CTMs) and chemistry-climate models (CCMs) became the best modelling tools to understand links between chemical and dynamical factors governing the formation, distribution and destruction of 55 stratospheric ozone Nowadays, these modelling tools include very detailed atmospheric chemistry processes, based on the most up-to-date scientific knowledge, and can provide very accurate simulations of stratospheric ozone (e.g. Eyring et al, 2007; Morgenstern et al, 2017).
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