The effect from chemical upper boundary conditions on tropospheric ozone in WRF-Chem

The changes in tropospheric ozone are mostly attributed to land-surface precursors emissions, advection of air, lightning activity and stratospheric air intrusion. The stratospheric intrusion is assumed as one of the most important natural sources of tropospheric ozone. In some regional numerical models of tropospheric composition ozone and other chemical species at the upper boundary is set from climatological data. This should be acceptable when the stratospheric composition does not change abruptly during a short period (month or less). However, it is not clear how the tropospheric ozone would change in the models in the conditions of such a phenomenon as stratospheric ozone anomalies.

In the current study we investigate the possible impact from stratospheric ozone sharp change on the tropospheric composition of the gas. For that the case of 2020 Arctic ozone anomaly is considered together with WRF-Chem numerical model of tropospheric state and composition. Four types of experiments were carried out - OLD-UBC and NEW-UBC-EAC4 and NEW-UBC-SOCOL. In the OLD-UBC experiment the standard monthly mean climatological data set of chemical species and tropopause pressure were used. In NEW-UBC-EAC4 and NEW-UBC-SOCOL the EAC4 reanalysis (ECMWF Atmospheric Composition Reanalysis 4) and SOCOL (SOlar Climate Ozone Links) global chemistry-climate model output for the simulated period (Jan - Jun 2020) were used with 1-day frequency to set upper boundary conditions in the WRF-Chem.