Arctic low-level mixed-phase clouds and their complex interactions with aerosol and radiation: Remote sensing of the Arctic troposphere with the shipborne supersite OCEANET-Atmosphere

• Published in: Atmospheric Measurement Techniques
• Main Author: Griesche, Hannes Jascha
• Other Authors: Universität Leipzig
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2021
• Subjects: Arctic Amplification; Shipborne remote sensing; Heterogeneous ice formation; Cloudnet; info:eu-repo/classification/ddc/530; ddc:530; Arctic; Mira
• Online Access: https://nbn-resolving.org/urn:nbn:de:bsz:15-qucosa2-797651; https://ul.qucosa.de/id/qucosa%3A79765; https://ul.qucosa.de/api/qucosa%3A79765/attachment/ATT-0/

In the course of this thesis, Arctic low-level mixed-phase clouds and their interaction with aerosol and radiation have been investigated. To do so, measurements with the shipborne remote sensing supersite OCEANET-Atmosphere were conducted during the PS106 expedition in the Arctic summer 2017. OCEANET-Atmosphere comprises among other instruments a multiwavelength polarization lidar PollyXT and a microwave radiometer HATPRO. For PS106 the OCEANET-Atmosphere facility was complemented for the first time with a motion-stabilized vertically pointing Doppler cloud radar Mira-35. The cloud radar Doppler velocity was corrected for the ship’s vertical movement. The stabilization and the correction enabled, e.g., the derivation of eddy dissipation rates from the Doppler velocities. A data set of cloud microphysical and macrophysical properties was derived by applying the synergistic Cloudnet algorithm to the combined measurements of cloud radar, lidar, and microwave radiometer. Within this thesis, the set of the Cloudnet retrievals was improved to account for the complex structure of the Arctic cloud system. A new detection approach for the frequently observed low-level stratus clouds was developed based on the lidar signal-to-noise ratio. These clouds, which were below the lowest range gate of the cloud radar were observed during 50 % of the observational time. A new approach for the continuous determination of the ice crystal effective radius was introduced. This new retrieval made the data set suitable to perform high-resolved radiative transfer simulations. The retrieved data set was utilized to derive the first temperature relationship for heterogeneous ice formation in Arctic mixed-phase clouds. A strong dependence of the surface coupling state for high subzero ice-formation temperatures was found. For an ice-formation temperature above -15 °C, surface-coupled ice-containing clouds occur more frequently by a factor of 5 in numbers of observed clouds and by a factor of 2 in frequency of occurrence. Possible causes of ...