COMPoSE: Characterization of phase partitioning in mixed-phase clouds

• Applicant: Dr. Heike Kalesse-Los
• Subject Area: Atmospheric Science
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 265895270

The formation and life cycle of mixed-phase clouds - in which supercooled liquid water droplets and solid ice crystals coexist - are poorly understood because making accurate mixed-phase cloud observations remains a challenge. Especially, the lack of a full vertical characterization of the distribution of supercooled liquid layers in mixed-phase clouds is one of the major deficiencies in widely applied observational methods. The proposed project is motivated by this existing gap in mixed-phase cloud observations and proposes a series of novel methods and models to tackle this complex problem. Mixed-phase cloud observations will be made with state-of-the-art high-resolution measurements with remote-sensing instruments such as cloud Doppler radar and Doppler- and polarization lidar. Synergistic profiling measurements with cloud radars and lidars to identify the liquid component of mixed-phase clouds are usually limited to the maximum lidar observation height which is determined by the complete signal attenuation at a penetrated optical depth of about three.In contrast, cloud radars are able to penetrate multiple liquid layers and could thus be used to expand the vertically resolved cloud phase identification in the entire vertical column beyond the lidar measurement range if appropriate algorithms to identify the liquid layer from radar measurements are developed. In the proposed project the full radar Doppler spectrum - which has a unique signature representing cloud microphysics and dynamics - will be analyzed in order to determine the phase partitioning in mixed-phase clouds in the entire vertical column beyond lidar extinction. Additionally, the radar Doppler spectra will be used to determine the vertical air motion to gain insight on cloud dynamics. The focus of this project will be on process studies at cloud scale, in particular on the analysis of the partitioning of the cloud thermodynamic phase in relation to temperature and vertical air motion as well as the development of this partitioning over time to gain insight into the life cycle of mixed-phase clouds. In that context, the impact of aerosols on the phase partitioning will be studied by segregation of the observed mixed-phase clouds according to the origin of the air masses via backward trajectory analysis and model forecasts and lidar measurements of aerosol properties. The proposed work extends beyond the development of remote sensing techniques. The use of a 1D microphysical model and of a radar Doppler spectra forward simulator will create a closed-loop that will allow us to evaluate our understanding of certain microphysical processes - such as riming - occurring in mixed-phase clouds.

• DFG Programme: Research Grants
• International Connection: Canada, USA
• Cooperation Partners: Professor Pavlos Kollias; Dr. Edward Luke; Dr. Wanda Szrymer