Rali-Thinice

RALI-THINICE aims at investigating the dynamics of Arctic cyclones (ACs) and tropopause polar vortices (TPVs), as well as their interactions with cloud microphysics, the underlying sea surface and sea ice in particular. A better knowledge of such processes should improve numerical weather predictions in the Arctic and should provide a better understanding of rapid sea ice loss events affecting the Arctic ice field in summer. The project relies on the comparison between Numerical Weather Prediction (NWP) simulations, satellite-derived observations (such as CloudSat and CALIPSO) and airborne observations made during an international field campaign in Svalbard in August 2022 involving American, French and British teams. The field campaign will involve two instrumented research aircraft. The ATR42 aircraft operated by SAFIRE (the French facility for airborne research) will be equipped with the remote sensing platform RALI, which is composed of a doppler cloud radar, a high-resolution backscatter lidar and an infrared radiometer. The aircraft will also contain in-situ microphysical probes. Measurements made by these instruments will help characterizing mixed-phase clouds that are ubiquitous in the Arctic and difficult to represent in state-of-the-art models. During the same period, the Twin Otter, the second aircraft to be deployed during the campaign by the British Antarctic Survey, will measure turbulent fluxes in the atmospheric boundary layer and concurrent sea ice surface properties beneath using remote sensing instruments. This will aim to characterise interactions between the sea ice and the lower troposphere. Coordinated flights will be planned between the two aircraft to take advantage of their complementary measurements. Different case studies will be performed to compare simulations of different global and regional atmospheric models with the observations. It will consist of simulating weather systems of interest, namely ACs, TPVs and moist intrusions, that will be or were observed during the future airborne field campaign in 2022 or during recent CloudSat-CALIPSO overpasses. Different sets of cloud microphysical schemes will be tested to analyze their effect on the distribution of hydrometeors in clouds. Their effect on atmospheric circulation will be also analyzed through the link between heating rates and potential vorticity modification. Similarly, the sensitivity to various parameters of sea ice – atmosphere coupling system will be tested to study the interactions between sea ice and ACs.