Characterization of Cirrus Cloud Properties by Airborne Differential Absorption and High Spectral Resolution Lidar Measurements

Abstract:

Despite the large impact of cirrus clouds on the Earth’s climate system, their effects are still only poorly understood. Our knowledge of the climate effect of cirrus clouds is mainly based on theoretical simulations using idealized cloud structure and microphysics, as well as radiative transfer approximations. To improve the representation of cirrus clouds in idealized simulations and circulation models, we need a better understanding of the micro- and macrophysical properties of cirrus clouds. Airborne lidar measurements provide two-dimensional information of the atmospheric structure, and are thus a suitable tool to study the fine-structure of cirrus clouds, as well as their macrophysical properties. Aerosol and water vapor was measured with the airborne high spectral resolution lidar (HSRL) and differential absorption lidar (DIAL) system WALES of the German Aerospace Center (DLR), Oberpfaffenhofen. The system was operated onboard the German high altitude and long range research aircraft HALO during the Next-generation remote sensing for validation studies campaign (NARVAL) in December 2013 over the tropical North-Atlantic and in January 2014 out of Iceland, and during the ML-Cirrus campaign in March/April 2014 over Central and Southern Europe. During NARVAL 18 flights with more than 110 flight hours were performed providing a large number of cirrus cloud overpasses with combined lidar and radar instrumentation. In the framework of the ML-Cirrus campaign 17 flights with more than 80 flight hours were performed to characterize cirrus cloud properties in different environmental conditions using a combination of remote sensing (e.g. lidar) and in-situ observations. In our presentation we will give a general overview of the campaigns and of the WALES measurements. We will show first results from the aerosol and water vapor lidar measurements with focus on the structure of cirrus clouds, the humidity distribution within and outside the cloud and on the impact of the stage of evolution on the cirrus cloud properties.