Impact of ECMWF ERA-Interim and ERA5 reanalysis on the simulated tracer transport and polar ozone loss using a chemical transport model TOMCAT/SLIMCAT 

<div> <p>Three-dimensional chemical transport models (CTMs) have been widely used in a wide variety of scientific studies (e.g., to obtain a better understanding of tracer transport and to study the dynamical and chemical processes which control polar ozone losses etc). However, there are still some uncertainties in the model simulations and indeed in our understanding. For example, the accuracy of ozone simulations largely depends on the transport, chemistry and treatment of PSCs in the model as well as the forcing files.&#160;</p> <p>Here we have used a&#160; CTM model TOMCAT/SLIMCAT with a detailed description of stratospheric and tropospheric chemistry forced by differnt wind fields (ECMWF ERA-Interim and <span>ERA5</span> reanalysis datasets) to investigate the different dynamical fields on the simulated tracer transport, ozone and other chemical species. Both simulations have been run from 1979 to 2018. First we will assess the impact of different reanalysis data on the idealised tracers when the model includes additional process of the gravitational separation of gases (e.g., Ar/N2) and compare the model results with dataset of gravitational fractionation of Ar/N2 and AoA observations made on flask samples from three airborne research projects. Modelled AoA will be also compared with MIPAS data.&#160; Then we will focus on the polar ozone loss from late 1990 to 2018 and quntify<br>the amount of chemical ozone loss using both models and satellite observations as well as&#160; SAOZ measurements. The year-to-year variation of polar ozone depletion will also be discussed, in particular for the recent years of decreasing stratospheric chlorine loading.&#160;</p> </div>