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This paper presents the unmanned research aircraft Carolo P360 "ALADINA"(Application of Light-weight Aircraft forDetecting IN situ Aerosol) for investigating thehorizontal and vertical distribution of ultrafine particles in theatmospheric boundary layer (ABL). It has a wingspan of 3.6 m, a maximumtake-off weight of 25 kg and is equipped with aerosol instrumentation andmeteorological sensors. A first application of the system, together with theunmanned research aircraft MASC (Multi-Purpose Airborne Carrier) of theEberhard Karls University of Tübingen (EKUT), is described. As smallpayload for ALADINA, two condensation particle counters (CPC) and one opticalparticle counter (OPC) were miniaturised by re-arranging the vital parts andcomposing them in a space-saving way in the front compartment of theairframe. The CPCs are improved concerning the lower detection threshold andthe response time to less than 1.3 s. Each system was characterised in thelaboratory and calibrated with test aerosols. The CPCs are operated in thisstudy with two different lower detection threshold diameters of 11 and 18 nm.The amount of ultrafine particles, which is an indicator for new particleformation, is derived from the difference in number concentrations of the twoCPCs (ΔN). Turbulence and thermodynamic structure of theboundary layer are described by measurements of fast meteorological sensorsthat are mounted at the aircraft nose. A first demonstration of ALADINA and afeasibility study were conducted in Melpitz near Leipzig, Germany, at theGlobal Atmosphere Watch (GAW) station of the Leibniz Institute forTropospheric Research (TROPOS) on 2 days in October 2013. There, variousground-based instruments are installed for long-term atmospheric monitoring.The ground-based infrastructure provides valuable additional backgroundinformation to embed the flights in the continuous atmospheric context and isused for validation of the airborne results. The development of the boundarylayer, derived from backscatter signals of a portable Raman lidarPOLLYXT, allows a quick overview of the current vertical structureof atmospheric particles. Ground-based aerosol number concentrations areconsistent with the results from flights in heights of a few metres. Inaddition, a direct comparison of ALADINA aerosol data and ground-basedaerosol data, sampling the air at the same location for more than 1 h, showscomparable values within the range of ± 20 %. MASC was operatedsimultaneously with complementary flight patterns. It is equipped with thesame meteorological instruments that offer the possibility to determineturbulent fluxes. Therefore, additional information about meteorologicalconditions was collected in the lowest part of the atmosphere. Verticalprofiles up to 1000 m in altitude indicate a high variability with distinctlayers of aerosol, especially for the small particles of a few nanometres indiameter on 1 particular day. The stratification was almost neutral and twosignificant aerosol layers were detected with total aerosol numberconcentrations up to 17 000 ± 3400 cm−3 between 180 and 220 maltitude and 14 000 ± 2800 cm−3 between 550 and 650 m. Apartfrom those layers, the aerosol distribution was well mixed and reached thetotal number concentration of less than 8000 ± 1600 cm−3. Duringanother day, the distribution of the small particles in the lowermost ABL wasrelated to the stratification, with continuously decreasing numberconcentrations from 16 000 ± 3200 cm−3 to a minimum of4000 ± 800 cm−3 at the top of the inversion at 320 m. Above this,the total number concentration was rather constant. In the region of 500 to600 m altitude, a significant difference of both CPCs was observed. Thisevent occurred during the boundary layer development in the morning andrepresents a particle burst within the ABL

atmospheric measurement techniques

ALADINA – an unmanned research aircraft for observing vertical and horizontal distributions of ultrafine particles within the atmospheric boundary layer