Non-uniform PSC occurrence within the Arctic polar vortex

A multi-year dataset of lidar measurements of polar stratospheric clouds (P SCs) from two sites in the Arctic (Sodankyla, 67 degreesN, 27 degreesE, and Ny-Angstrom lesund, 79 degreesN, 12 degreesE) has been analyzed with respe ct to the existence temperature of different PSC types. Due to the location of the measurement sites relative to the polar vortex, their observations are most of the time representative of vortex edge and vortex center condit ions, respectively. The comparison of the aerosol lidar measurements with l ocal and trajectory temperatures reveals that PSC occurrence is favored at the edge of the Arctic polar vortex. One possibility discussed here is a di fferential distribution of water vapor that could be responsible for the no n-uniform threshold temperatures and thus differential PSC occurrence withi n the polar vortex.