BE-7 AND PB-210 INDICATE AN UPPER TROPOSPHERE SOURCE FOR ELEVATED OZONE IN THE SUMMERTIME SUBTROPICAL FREE TROPOSPHERE OF THE EASTERN NORTH-ATLANTIC

The relative abundance of Be-7 and Pb-210 in aerosols, represented as the ''normalized fraction'', Be-7/(Be-7 + n(210)Pb), is unaffected by aerosol scavenging. This normalized fraction is an index of the relati ve influence on an air parcel of stratospheric and upper tropospheric processes versus those in the continental boundary layer (CBL). The hi gh correlation of ozone concentration with the normalized fraction obs erved during the summer at Izana, Canary Islands, indicates that 1) lo w altitude transport of air from the CBL is associated with low ozone concentrations; 2) high altitude transport through the troposphere fro m the CBL is associated with net ozone production; and 3) the stratosp here is not a direct source of a significant fraction of the ozone obs erved at Izana during the summer.