CHARLICE – Compact Heterodyne Aerosol Rayleigh–Brillouin Lidar at 532 nm wavelength for the observation of ice formation processes

• Applicant: Dr. Ronny Engelmann
• Subject Area: Atmospheric Science
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 539150939

Doppler lidars for wind measurements are often applied in meteorology and in the energy sector. A distinction is made between Doppler lidars with direct detection (using spectrometers) and heterodyne detection (using superposition of two light sources). Systems with direct detection, e.g., the space lidar ALADIN, mostly operate in the ultraviolet wavelength range and have the advantage of providing a signal by scattering at air molecules even in a particle-free atmosphere. However, the measurement error is often several meters per second. Heterodyne systems operate in the infrared wavelength range and achieve wind speed accuracies of several centimeters per second. Such devices are already commercially available and are used in a variety of applications. In cooperation with three industrial partners, TROPOS has developed a new type of Doppler lidar that combines the advantages of both systems, operates at a wavelength of 532 nm, and uses heterodyne detection. The use of visible light is an absolute novelty, since for the first time also a molecular signal can be measured in a particle-free atmosphere with this type of lidar. It is also possible to calibrate a spectrally resolved particle backscatter signal using the molecular signal. TROPOS intensively studies cloud formation processes. Mixed-phase clouds and their microphysical properties are the focus of interest. With this lidar, the extinction of ice crystals will be measured spectrally resolved for the first time, i.e., also size-separated due to the different falling velocities of the ice crystals. In combination with a Doppler cloud radar, the size spectrum of ice particles in mixed phase clouds will then be derived. Compared to previous approaches, an a priori assumption on the ice particle spectrum is then no longer necessary. Equally novel is the intent to use this lidar to detect wind in particle-free air (e.g., in the free troposphere). For these tasks, a PhD position is requested in the present application. Currently, Felix Fritzsch is working intensively on this Doppler lidar as part of his Master's thesis. However, further technical steps are necessary to achieve and evaluate the full performance of the system. The first part of the PhD project will, therefore, deal intensively with still necessary technical developments, while the second and third parts will focus on measurements and the investigation of the microphysics of ice crystals.

• DFG Programme: Research Grants
• Co-Investigator: Dr. Johannes Bühl