November 2007
The events of the 27th and 30th November were part of a wave disturbance of a sequence of high and low events. It was not a severe mini-hole but recorded by both satellite and ground-based instruments. Figure A below shows the anomaly on the 27th and a mini-hole to the east of the US is clearly already visible. This wave disturbance was advected to the east so that a further mini-hole appeared on the 30th (Figure B). Reading reported daily mean ozone of 227 DU and 222 DU on the 27th and 30th . These events are confirmed by the Manchester readings of 220 DU and 188 DU respectively. The OMI satellite reports 232 and 213 DU respectively. There is therefore overall all reasonable agreement with the satellite for this event.
The autumn has seen an active storm generation in the mid-Atlantic coupled with persistent anti-cyclonic conditions over the UK. These conditions are favourable for mini-holes over the UK. The frequency may be explicable by the natural low seasonal amount of ozone and an unexplained long-term decline in this season.
Figure A: Ozone anomaly on the 27th November 2007.
Figure B: Ozone anomaly on the 30th November 2007.
On the 7th of November there was minor event (less than 1% below the alert threshold at Reading). This anomaly was first generated off the coast of Greenland and then advected westwards over the entire UK. It has its tropospheric origin in a tropospheric anticyclone near Spain. This caused tropopause lifting and advection of poor ozone air. This relatively minor anomaly intensified over France.
The events of the 27th and 30th November were part of a wave disturbance of a sequence of high and low events. It was not a severe mini-hole but recorded by both satellite and ground-based instruments. Figure A below shows the anomaly on the 27th and a mini-hole to the east of the US is clearly already visible. This wave disturbance was advected to the east so that a further mini-hole appeared on the 30th (Figure B). Reading reported daily mean ozone of 227 DU and 222 DU on the 27th and 30th . These events are confirmed by the Manchester readings of 220 DU and 188 DU respectively. The OMI satellite reports 232 and 213 DU respectively. There is therefore overall all reasonable agreement with the satellite for this event.
The autumn has seen an active storm generation in the mid-Atlantic coupled with persistent anti-cyclonic conditions over the UK. These conditions are favourable for mini-holes over the UK. The frequency may be explicable by the natural low seasonal amount of ozone and an unexplained long-term decline in this season.
Figure A: Ozone anomaly on the 27th November 2007.
Figure B: Ozone anomaly on the 30th November 2007.
On the 7th of November there was minor event (less than 1% below the alert threshold at Reading). This anomaly was first generated off the coast of Greenland and then advected westwards over the entire UK. It has its tropospheric origin in a tropospheric anticyclone near Spain. This caused tropopause lifting and advection of poor ozone air. This relatively minor anomaly intensified over France.