We. Davies et al., OBSERVATION OF NEAR-ZERO OZONE CONCENTRATIONS IN THE UPPER TROPOSPHERE AT MIDLATITUDES, Geophysical research letters, 25(8), 1998, pp. 1173-1176
Measurements by an ECC ozonesonde launched from Aberystwyth (52.4 degr
ees N, -4.1 degrees E) in July show ozone concentrations decreasing st
eadily from a warm frontal surface to the tropopause, cumulating in a
layer similar to 0.5 km deep with near-zero ozone concentrations at 12
km. Such features have previously been detected by lidar but have not
been reported in ozonesonde data at mid-latitudes; they have, however
, been found in ozonesonde profiles above the equatorial Pacific. We e
xamine three possible hypotheses for the origin of the ozone-free air:
in situ destruction by cirrus clouds, rapid transport from the marine
boundary layer in the extratropics and long-range transport from the
tropics. We conclude that the ozone-poor air observed on this day coul
d only have resulted from long-range transport from the tropics.