MEASUREMENT OF OZONE DURING POLAR SUNRISE EXPERIMENT 1992

Surface level ozone was measured continuously for the period January-A pril 1992 at two sites near Alert, Northwest Territories, Canada. Also , vertical profiles of ozone and meteorological parameters were measur ed at Alert with tethersondes for a selected period in April. Three oz one depletion events with ozone <0.5 ppb were recorded during April; t ethersonde data were available for one of these events. Except for the se ozone depletions the surface ozone concentration was lowest in Janu ary, in the range 25-30 ppb, and then progressively increased to a hig h in April, in the range of 40-45 ppb. Analysis of the present and som e past ozone profile data from upper air sondes showed that ozone depl etion at polar sunrise was associated with a neutral potential tempera ture profile within the boundary layer (i.e., low stability) capped by an elevated inversion at several hundred meters above the surface.