GOME measurements from the last three winter/spring seasons 1995/1996, 1996/1997, and 1997/1998 are available. Selected monthly total ozone means for the two recent winter/spring seasons, which were derived from the GOME level-2 Version 2.0 ozone data, are shown in Fig. 1, which reveals the high year-to-year variability in the dynamics of the total ozone in the northern hemisphere. The typical winter/spring ozone maximum expected for high northern latitude is exemplified by the values of more than 400 DU observed above the Sea of Ohkotsk (Far East) and above Hudson Bay (Canada), which is linked to preferred cyclone activity in these regions. Low ozone values, which occasionally drop below 300 DU, are detected above the North Atlantic and Northern Europe. Particularly in March/April 1997 mean ozone levels were low inside the polar vortex. In February and March 1998, the mean ozone levels were higher than in the previous years, which agrees with the generally higher observed stratospheric temperatures at the 50hPa pressure level which were closer to the longterm mean and higher than in the previous three years (L. McCoy, NASA, private communications).
Figure: GOME total ozone monthly means for February, March and April 1997 (upper panel) and February and March 1998 (lower panel). The stereographic projection extends from the North Pole to 40 deg N. GOME level-2 data Version 2.0 were used to derive the monthly means for 1997 and Version 3.0 for 1998.