Low ozone over the UK

Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion EGU Abstract A record low total ozone column of 177 DU was observed at Reading, UK, on 19 Jan-uary 2006. Low ozone values were also recorded at other stations in the British Isles and North West Europe on, and around, this date. Hemispheric maps of total ozone from the World Meteorological Organisation (WMO) Ozone Mapping Centre also show 5 the evolution of this ozone minimum from 15–20 January 2006 over North West Eu-rope. Ozonesonde measurements made at Lerwick, UK, show that ozone mixing ratios in the mid-stratosphere on 18 January are around 1–2 ppmv lower than both climatology and observations made one and two weeks prior to this date. In addition, ozone mixing 10 ratios in the UTLS region were also noticeably reduced on 18 January. Analysis of the ozonesonde observations indicate that the mid-stratosphere ozone accounts for around a third of the reduction in total ozone column measurements while the UTLS ozone values account for two thirds of the depletion. It is evident from the ozonesonde data that ozone loss is occuring at two distinct vertical regions. 15 Met Office analyses indicate that stratospheric polar vortex temperatures were cold enough for Polar Stratospheric Cloud (PSC) formation during 14 days in January prior to the low ozone event on 19 January. The presence of PSCs is confirmed by observations from the Scanning Imaging Absorption spectroMeter for Atmospheric Cartogra-pHY (SCIAMACHY). As a consequence of a stratospheric sudden warming that was in 20 progress during January 2006, the polar vortex was shifted southwards over northwest Europe. This includes a period from 16 to 19 January where PSCs were present in the vortex over the UK. Throughout most of January suitable conditions were present for ozone destruction by heterogenous chemistry within the polar vortex. Evidence from Lerwick and Sodankyï a ozonesonde profiles, and maps of Ertel's potential vorticity cal-25 culated from Met Office analyses, strongly suggests that the air inside the stratospheric vortex was poor in ozone for at least one week prior to 18 January. It is also possible that local chemical destruction of stratospheric ozone further contributed to the record 8458 Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion EGU low ozone observed at Reading. A closer examination of the WMO total ozone maps shows that the daily …