Stefano Casadio

Observation of polar stratospheric clouds with the ABLE LIDAR during the APE-POLECAT flight of January 9, 1997

Observations of Polar Stratospheric Clouds (PSCs) were carried out with an airborne lidar on the stratospheric M55 Geophysica aircraft during a .ight from Rovaniemi, Finland, on 9 January, 1997. The clouds were observed at the zenith, downwind from the Norwegian Alps: three PSCs, of somewhat di=erent characteristics, were detected at heights between 23 and 28 km. In two of the clouds, di=erent types of particles seem to coexist: echoes attributable to types I and II PSCs are found in di=erent portions of the clouds. The formation of the PSCs is related to an orographic lee-wave, whose development was forecast by a mesoscale dynamical model used to plan the .ight path. The largest observed PSC displays a complex structure, that appears to be in.uenced by waves of di=erent wavelengths. In particular, lidar and in situ data suggest the presence of a wave having a relatively short length (about 18 km) that overlaps on the main lee-wave. The short wavelength oscillation is thought to play a major role in the cloud development, determining the rapid formation and evaporation of particles and therefore the non-stationary character of the PSC. ? 2003 Elsevier Science Ltd. All rights reserved.

Determination of stratospheric temperature and density by GOMOS: Verification with respect to high latitude LIDAR profiles from Thule, Greenland

High resolution temperature profiles (HRTP) have been derived from measurements performed by Global Ozone Monitoring by Occultation of Stars (GOMOS) onboard ENVISAT. HRTP are derived from measurements with two fast photometers whose signal is sampled at 1 kHz, and allows investigating the role of irregularities in the density and temperature profiles, such as those associated with gravity waves. In this study high resolution temperature and density profiles measured at high latitude by GOMOS are compared with observations made with the ground-based aerosol/temperature LIDAR at Thule, Greenland. The LIDAR at Thule contributes to the Network for the Detection of Atmospheric Composition Change. The LIDAR profiles are analyzed in the height interval overlapping with GOMOS data (22-35 km), and the density and temperature profiles are obtained with 250 m vertical resolution. The comparison is focused on data collected during the 2008-2009 and 2009-2010 Arctic winters. Profiles measured within 6 hours and 500 km...