Model-guided Lagrangian observation and simulation of mountain polar stratospheric clouds

Gravity-wave-induced polar stratospheric clouds (PSCs) were observed over t he Scandinavian mountains by airborne lidar on January 9, 1997. Guided by t he forecasts of a mesoscale dynamical model, a flight path was chosen to le ad through the coldest predicted region parallel to the wind at the expecte d PSC level (23-26 km). Because of the nearly stationary nature of the wave -induced PSC the individual filaments visible in the backscatter data of th e clouds can be interpreted as air parcel trajectories. Assuming dry adiaba tic behavior and fixing the absolute temperature to the ice frost point in the ice part of the cloud enables detailed microphysical simulations of the whole life cycle of the cloud particles. Optical calculations are used to adjust open parameters in the microphysical model by optimizing the agreeme nt with the multichannel lidar data. This case is compared with former work from the Arctic winter 1994/1995. The influence of the stratospheric H2SO4 content and the cooling rate on the type of cloud particles (liquid ternar y solution droplets or solid nitric acid hydrates) released from the ice pa rt of the cloud is evaluated.