October 2004 at Lerwick
The October 31st value of 189 DU (TOMS reported 198 DU) is the lowest daily ozone value recorded at Lerwick at least since 1981. Inspection of meteorological analysis confirmed standard features of mini-hole dynamics i.e. tropopause lifting (high tropopause pressure) and strong advection of ozone poor air from the south near the tropopause. The figure below shows the TOMS map for October 31st.
It should be noted that the Lerwick observation was based on only 4 zenith sky measurements. Nevertheless, the TOMS record confirms two severe ozone mini holes over the North Atlantic and a simultaneous hole over Finland. The double hole structure is somewhat unusual. On the 29th September Lerwick was at the edge of the mini hole, but on the 31st October it was closer to the centre of it. Ozone values over the rest of the UK were not exceptionally low on either day.
The October 31st value of 189 DU (TOMS reported 198 DU) is the lowest daily ozone value recorded at Lerwick at least since 1981. Inspection of meteorological analysis confirmed standard features of mini-hole dynamics i.e. tropopause lifting (high tropopause pressure) and strong advection of ozone poor air from the south near the tropopause. The figure below shows the TOMS map for October 31st.
It should be noted that the Lerwick observation was based on only 4 zenith sky measurements. Nevertheless, the TOMS record confirms two severe ozone mini holes over the North Atlantic and a simultaneous hole over Finland. The double hole structure is somewhat unusual. On the 29th September Lerwick was at the edge of the mini hole, but on the 31st October it was closer to the centre of it. Ozone values over the rest of the UK were not exceptionally low on either day.