Ground-based DOAS measurements of stratospheric trace gases at two Antarctic stations during the 2002 ozone hole period

Compared to recent years, the development of the Antarctic ozone hole in 2002 showed very unusual dynamical features. The midwinter polar vortex was one of the smallest observed during the past decade. Driven by planetary waves, the vortex showed a strong asymmetry in early spring. A large air mass separated in late September, leaving what was previously a small vortex even smaller. Furthermore, stratospheric temperatures exceeded the polar stratospheric cloud (PSC) threshold earlier than in previous years, leading to a decrease in halogen activation by heterogeneous surface reactions. Ground-based observation of stratospheric trace gases in austral spring of 2001 and 2002 using passive Differential Optical Absorption Spectroscopy (DOAS) observations of zenith-scattered sunlight in the UV and visible wavelength region (320-650 nm) are presented. Using DOAS measurements of ozone, N[O.sub.2], BrO, and OCIO at two different Antarctic sites, Neumayer Station (70[degrees]S, 8[degrees]W) and Arrival Heights (78[degrees]S, 167[degrees]E), the chemical composition of the stratosphere is investigated under the unusual conditions of the 2002 ozone hole period and compared to the more typical observations of the previous year (2001).