Project Details
Projekt
Polarimetric Radar Signatures of Ice Formation Pathways from Controlled Aerosol Perturbations (PolarCAP)
Applicants
Dr. Patric Seifert; Dr. Fabian Senf
Subject Area
Atmospheric Science
Term
since 2018
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 408027490
A multitude of processes is involved in the evolution of cloud systems under slightly supercooled conditions down to -10°C. The interaction of thermodynamics, water vapour and aerosol particles controls the phase partitioning, precipitation formation and radiative properties, but the associated pathways can hardly be disentangled. The proposed project PolarCAP aims at tackling the complex problem by exploring the evolution of the ice phase at slightly supercooled conditions in a thermodynamically and aerosol-controlled natural environment using radar polarimetry and spectral-bin modelling. Target of the study are predominantly liquid supercooled stratiform cloud layers which frequently form during wintertime in the temperature range from -10 to 0°C over the Swiss Plateau. In the frame of the external ERC research project CLOUDLAB, drones will be used to seed these clouds with defined amounts of different types of ice nucleating particles, such as silver iodide or Snowmax. The subsequently formed ice phase and decay of the liquid phase will be characterized within CLOUDLAB using in-situ measurements and a standard set of remote sensing instrumentation such as lidar and LDR-mode cloud radar, with the goal to improve 1-moment and 2-moment ice-phase parameterisations of the numerical weather prediction model ICON. PolarCAP will collaborate with the CLOUDLAB project in order to enhance and utilize the unique dataset by means of the application of cutting-edge polarimetric radar- and lidar-based remote sensing techniques for the determination of cloud microphysical properties, as well as the application of cloud-resolving spectral-bin modelling. Synergistic, multi-wavelength and polarimetric ground-based remote sensing with scanning radar and lidar will be used to monitor the transition of supercooled liquid stratiform clouds into mixed-phase clouds. Accompanied by cloud-resolving model simulations and radar forward operators, PolarCAP will trace the evolution and involved microphysical processes of the phase partitioning in the low-supercooling temperature range between -10 and 0°C. The combined observations will yield new insights into the interplay of contact and immersion freezing, secondary ice formation and ice multiplication, by investigating clouds in different temperature regimes which are presumed to be either affected or unaffected by specific ice-phase processes. The investigations in PolarCAP provide challenges for our current cloud-microphysical process understanding and its representation in atmospheric models. The project will therefore advance cloud-resolving modelling and its coupling to radar forward operators. Overall, PolarCAP will achieve progress in the ability to constrain the efficiency of different ice nucleating substances and to link the time scales of microphysical process and stratus dissipation.
DFG Programme
Priority Programmes
