Studying differences in microphysics of ice clouds in the Arctic depending on airmass origin using lidar-radar synergy

The climate in the Arctic is changing rapidly. The near-surface air temperature increased much faster than on global average in recent years, a phenomenon called Arctic Amplification. This Arctic Amplification leads to a weaker and wavier jet stream, potentially allowing a more frequent transport of airmasses into the Arctic which have their origin in the mid-latitude. These mid-latitude airmasses are responsible for an influx of warm and moist air, significantly influencing the energy budget in the Arctic due to their radiative effects. But airmass transport from the mid-latitudes has also an impact on cloudiness in the Arctic as well as on cloud properties, as they strongly depend on the conditions under which the clouds form. The main focus on cloud so far, however, was on lower-level clouds. Arctic high level ice clouds are hard to study. Satellite measurements do often not provide data with sufficient accuracy or resolution, and in-situ measurement have rarely been performed.

 

In March and April 2022, the HALO-(AC)³ campaign was conducted, using the German High Altitude and LOnge range (HALO) research aircraft equipped with a remote sensing payload. With HALO it was possible to perform high altitude measurements deep inside the Arctic. The measurements provided high accurate and highly resolved information about the atmosphere along the flight path. Key instruments during HALO-(AC)³ have been the combined airborne water vapor differential absorption and high spectral resolution lidar WALES, and the Doppler cloud radar MIRA-35. We use the measurements of the lidar to characterize the environmental conditions in Arctic and mid-latitude airmasses, i.e. the humidity field. Ice cloud microphysical properties are derived from the synergy of lidar and radar using an optimal estimate retrieval. The combination of the characterization of the environmental conditions and the cloud properties allows to study differences in the microphysics of ice clouds in the Arctic depending on the origin of the airmasses they are forming in. We will give an overview of our measurements, the characterization of the environmental conditions, and will show differences in the cloud macro- and microphysical properties of the observed ice clouds.