Testing aerosol vertical profiling methods with portable instruments on unmanned and manned aircraft

Abstract: This thesis employed several portable sensors on board an unmanned aerial vehicle (UAV) and manned aircraft in order to test new methods of measuring vertical profiles of aerosol particles and contribute to knowledge of aerosol distributions in the atmosphere. More data in this area is required to improve atmospheric modelling and future climate scenarios. The handheld nanoparticle detector Partector 2, miniature aethalometer MA300, low-cost optical particle counter (OPC)-N3, and the portable aerosol spectrometer 11-D were used to measure the total number concentration of nanoparticles, the mass concentration of black carbon (BC), and the PM2.5 mass concentration. At the rural background monitoring site Hyltemossa, sensors compared well to reference instruments in most cases and a total of seven vertical profiles up to a maximum altitude of 165 m were performed with the UAV over two days (10-11th October 2022). Measurements were conducted both within/above the forest canopy and over a nearby cleared area, but no evidence was found to suggest that the canopy directly influenced the vertical aerosol distribution. However, notable differences in the resulting concentration profiles were observed between the two days, which could be linked to different air mass origins. During measurements onboard two manned instructional flights (operated by the Lund School of Aviation based in Ljungbyhed) on the 13th October, similar vertical profiles were observed during ascent and descent, despite over 200 km separation. A notable reduction in aerosol concentrations was observed from around 1500 m altitude, suggesting the plane crossed the planetary boundary layer (PBL). The methods used in this thesis were considered viable with a few improvements, such as a dryer for UAV-based sensors and a better sampling inlet for aircraft measurements. Using UAVs and instructional aircraft as platforms for portable sensors are promising techniques for regular vertical profile measurements, and future campaigns are expected to further increase understanding of aerosol distributions and related atmospheric processes.