Investigation of ice particle and cloud drop residues using the counterflow virtual impactor technique onboard the new German research aircraft HALO

The subset of atmospheric particles which serve as cloud condensation and ice nuclei (CCN and IN) determine the aerosol indirect effect, which has one of the largest uncertainties in predicting future climate. Especially the influence of anthropogenic particles on microphysical properties of liquid, mixed-phase and glaciated clouds and thus on their radiative properties and precipitation behavior is not well understood. The identification of CCN and IN, measured as residues of drops and ice particles of different cloud types by airborne counterflow virtual impactors (CVI) was successfully carried out in the past. This will be now combined with the long range, long endurance, high altitude and large scientific payload capabilities of the new German research aircraft HALO. This inlet system (HALO-CVI) that samples liquid and frozen hydrometeors and releases the contained residues for analysis is designed for the special flight conditions of HALO. It will be applied as part of the designated scientific payload of three HALO cloud missions investigating the influence of aerosol particles on the formation and evolution of aviation modified and natural cirrus (ML-CIRRUS mission), extra-tropical deep convective cloud systems (ACRIDICON mission) and trade wind cumuli (NARVAL mission). Beside the sampled condensed water content, the number concentration, size distribution and black carbon content of the drop and ice particle residuals will be measured downstream the HALO-CVI. Moreover, CCN and IN activation capabilities, hygroscopic growth and single-particle chemical composition of the residues will be determined with state-of-the-art instrumentation of other institutions collaborating within the HALO cloud missions. Detailed information about the HALO-CVI, the coupled instrumentation and about the different missions concerning target area, flight pattern, and measurement strategy will be presented.