SUMMER AND SPRING OZONE PROFILES OVER THE NORTH-ATLANTIC FROM OZONESONDE MEASUREMENTS

Ozone profiles obtained by near-daily ozonesonde observations during c ampaigns at several sites in the North Atlantic are used to construct time-height cross sections of ozone concentration through the troposph ere, Strong day-to-day ozone variability on the scale of synoptic mete orological disturbances is found both in the spring and in the summer throughout much of the troposphere. Layers of high ozone concentration (similar to 100 ppb) are frequently seen in the middle and upper trop osphere and are invariably associated with transport characteristics t hat strongly support a stratospheric source for these layers. Regions of low ozone (<40 ppb) are seen in the middle and upper troposphere as sociated with higher relative humidity. The connection of these events with low surface mixing ratios suggests that convective processes mix air low in ozone up through the troposphere. Vertical layering of ozo ne mixing ratio, which is seen at all of the observing locations, is a result of differing sources of air in the different layers.