CAMP: an instrumented platform for balloon-borne aerosol particle studies in the lower atmosphere

Airborne observations of vertical aerosol parti-cle distributions are crucial for detailed process studies and model improvements. Tethered balloon systems represent a less expensive alternative to aircraft to probe shallow atmospheric boundary layers (ABLs). This study presents the newly developed cubic aerosol measurement platform (CAMP) for balloon-borne observations of aerosol particle microphysical properties. With an edge length of 35 cm and a weight of 9 kg, the cube is an environmentally robust in-strument platform intended for measurements at low tem-peratures, with a particular focus on applications in cloudy Arctic ABLs. The aerosol instrumentation on board CAMP comprises two condensation particle counters with differ-ent lower detection limits, one optical particle size spec-trometer, and a miniaturized absorption photometer. Com-prehensive calibrations and characterizations of the instru-ments were performed in laboratory experiments. The first field study with a tethered balloon system took place at the Leibniz Institute for Tropospheric Research (TROPOS) sta-tion in Melpitz, Germany, in the winter of 2019. At ambient temperatures between -8 and 15 ?C, the platform was op-erated up to a 1.5 km height on 14 flights under both clear-sky and cloudy conditions. The continuous aerosol observa-tions at the ground station served as a reference for evalu-ating the CAMP measurements. Exemplary profiles are dis-cussed to elucidate the performance of the system and pos-sible process studies. Based on the laboratory instrument characterizations and the observations during the field cam-paign, CAMP demonstrated the capability to provide com-prehensive aerosol particle measurements in cold and cloudy ABLs.