Characterisation of subcloud sublimation of precipitation at Neumayer Station III in Antarctica (CASSIOPEIA)

• Applicant: Professorin Dr. Heike Kalesse-Los
• Subject Area: Atmospheric Science
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 561848493

Precipitation is an essential component of the Antarctic climate system as part of the hydrological cycle, thus linking the atmosphere and cryosphere through snowfall (and rarely rain). Specifically, precipitation is the most important positive contributor of the Antarctic ice sheet mass balance. In a progressing warming climate, precipitation in Antarctica is expected to increase. Snowfall in Antarctica is not well quantified because of the sparsity of observations due to the challenging environment, e.g. strong katabatic winds creating blowing snow in coastal regions. Katabatic winds also lead to the presence of dry subcloud layers, so that a non-negligible amount of Antarctic precipitation sublimates before reaching the ground. At the same time, due to ground clutter, the lowest reliable measurement height of satellite-borne radars over land is about 1.2 km for CloudSat and about 0.8 km for EarthCare. Thus, satellite-borne radar precipitation retrievals overestimate precipitation in areas where significant subcloud sublimation occurs. Atmospheric sublimation is however an important process as it cools and moistens the subcloud layer thus influencing atmospheric stability and the surface radiative budget. We here propose to for the first time characterize the vertical precipitation structure above the Ekström ice shelf on the coast of Dronning Maud Land at Neumayer station III and to assess how often and how much precipitation sublimates below cloud base before falling onto the ice shelf. For that purpose, we will exploit synergistic long-term ground-based atmospheric remote sensing data sets obtained by cloud radar, lidar, microwave radiometer, and micro rain radar at Neumayer III station within the frame of the project SPP-1158 project COALA (observations from Jan to Dec 2023) which were continued by the Alfred-Wegener-Institute (AWI) as of January 2024. We also plan to evaluate how snowfall properties itself like terminal fall velocity and density and environmental factors (including temperature, humidity, and wind) influence atmospheric sublimation. Furthermore, we aim to quantify the overestimation of surface precipitation by satellite-borne radar estimates. The proposed project will be embedded in the overarching SPP1158 research question of improving the understanding of polar processes and mechanisms. Among others, we plan to collaborate with the SPP1158 projects COALA (PL: M. Radenz, P. Seifert, TROPOS) as well as VACCINE+ (PL: S. Henning) regarding relating sublimation characteristics to precipitation formation processes and air mass origins and respective concentrations of ice nucleating particles and cloud condensation nuclei.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1158: Infrastructure area - Antarctic Research with Comparative Investigations in Arctic Sea Ice Areas
• International Connection: Portugal, Switzerland
• Cooperation Partners: Professor Dr. Alexis Berne; Dr. Irina Gorodetskaya
• Co-Investigator: Dr. Martin Radenz