MECHANISMS FOR SURFACE OZONE DEPLETION AND RECOVERY DURING POLAR SUNRISE

As part of the Polar Sunrise Experiment (PSE 94) in April 1994, vertic al profiles of ozone concentration, temperature and wind speed above a n Arctic Ocean icefloe were obtained to investigate boundary layer ozo ne depletion. They show sustained periods of depleted surface ozone (< 1 ppbv) in a layer 300 to 400 m deep. A one-dimensional model was appl ied to the data in an attempt to determine the magnitude of chemical d estruction rates. The rate of change of ozone corresponding to the com bined result of horizontal advection and a volume or a surface sink wa s calculated to be in the range of -0.001-0.001 ppbv s(-1) while the s urface deposition velocity was estimated, for most cases, to be in the range of 0.006-0.016 cm s(-1). Generally, at this fixed observational point, air mass changes and associated horizontal advection were domi nant factors in controlling ozone change. If weak chemical sink rates are to be separated from strong advection changes, future studies will have to take special care to define the horizontal gradient of ozone. Copyright (C) 1997 Elsevier Science Ltd.