23 Aug 2023
 | 23 Aug 2023
Status: this preprint is currently under review for the journal AMT.

Two new multirotor UAVs for glaciogenic cloud seeding and aerosol measurements within the CLOUDLAB project

Anna J. Miller, Fabiola Ramelli, Christopher Fuchs, Nadja Omanovic, Robert Spirig, Huiying Zhang, Ulrike Lohmann, Zamin A. Kanji, and Jan Henneberger

Abstract. Uncrewed Aerial Vehicles (UAVs) have become widely used in a range of atmospheric science research applications. Because of their small size, flexible range of motion, adaptability, and low cost, multirotor UAVs are especially well-suited for probing the lower atmosphere. However, their use so far has been limited to conditions outside of clouds, first because of the difficulty of flying beyond visual line of sight, and second because of the challenge of flying in icing conditions in supercooled clouds. Here, we present two UAVs for cloud microphysical research: one UAV (the measurement UAV) equipped with a Portable Optical Particle Spectrometer (POPS) and meteorological sensors to probe the aerosol and meteorological properties in the boundary layer, and one UAV (the seeding UAV) equipped with seeding flares to produce a plume of particles that can initiate ice in supercooled clouds. A propeller heating mechanism on both UAVs allows for operating in supercooled clouds with icing conditions. These UAVs are an integral part of the CLOUDLAB project in which glaciogenic cloud seeding of supercooled low stratus clouds is utilized for studying aerosol-cloud interactions and ice crystal formation and growth. In this paper, we first show validations of the POPS onboard the measurement UAV, demonstrating that the rotor turbulence has a negligible effect on aerosol measurements. We exemplify its applicability for profiling the planetary boundary layer, as well as for sampling and characterizing aerosol plumes, in this case, the seeding plume. We explain the different flight patterns that are possible for both UAVs, namely horizontal or vertical leg patterns or hovering, with an extensive and flexible parameter space for designing the flight patterns according to our scientific goals. Finally, we show two examples of seeding experiments: first characterizing an out-of-cloud seeding plume with the measurement UAV flying horizontal transects through the plume, and second, characterizing an in-cloud seeding plume with downstream measurements with POPS on a tethered balloon. Particle concentrations and size distributions of the seeding plume from the experiments reveal that we can successfully produce and measure the seeding plume, both in-cloud and out-of-cloud. The methods presented here will be useful for probing the lower atmosphere, for characterizing aerosol plumes, and for deepening our cloud microphysical understanding through cloud seeding experiments, all of which have the potential to benefit the atmospheric science community.

Anna J. Miller et al.

Status: open (until 27 Sep 2023)

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  • RC1: 'Comment on amt-2023-157', Anonymous Referee #1, 12 Sep 2023 reply

Anna J. Miller et al.

Anna J. Miller et al.


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Short summary
We present a method for aerosol and cloud research using two uncrewed aerial vehicles (UAVs). The UAVs have a propeller heating mechanism that allows flights in icing conditions, which has so far been a limitation for cloud research with UAVs. One UAV burns seeding flares, producing a plume of particles that causes ice formation in supercooled clouds. The second UAV measures aerosol size distributions and is used for measuring the seeding plume or for characterizing the boundary layer.