Record low ozone values over the Arctic in boreal spring 2020

Abstract. Ozone data derived from the Tropospheric Monitoring Instrument (TROPOMI) sensor on board Sentinel-5 Precursor satellite show exceptionally low total ozone columns in polar region of Northern Hemisphere (Arctic) spring 2020. Minimum column values around or below 220 Dobson units (DU) were seen over Arctic for 5 weeks March and early April Usually persistence such is only observed Southern (Antarctic) not Arctic. These record caused by a particularly strong vortex stratosphere with persistent cold at higher latitudes, prerequisite depletion through heterogeneous chemistry. Based ERA5, which fifth generation European Centre Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis, winter 2019/2020 (from December to March) showed minimum cap temperatures consistently 195 K 20 km altitude, enabled enhanced formation stratospheric clouds. The special situation 2020 compared discussed context two other seasons, namely those 1997 2011, also displayed relatively values. However, during these years, DU several consecutive days spring. similarities differences conditions three events possible explanations features are presented discussed. It becomes apparent that monthly mean value (221 DU) was clearly respective found (267 2011 (252 DU), highlights evolution layer A comparison typical hole Antarctic (e.g., 2016) indicates although remarkable, considerable area (up 0.9 million km2), shows typically 150 much larger (of order km2). Furthermore, about 4 months.