44 research outputs found
Miniature high-frequency chilled-mirror hygrometer for atmospheric measurements aboard fixed wing UAS
A small light-weight in-house made miniature chilled-mirror hygrometer (CMH) for fixed wing UAS (unmanned aircraft system) is presented, with its features and limitations. Therefore, first measurements of the CMH equipped on the small research UAS of type MASC‑3 (multi-purpose airborne sensor carrier) operated by the University of Tübingen are shown. A comparison against a very accurate state of the art capacitive industrial humidity sensor (SHT31) is done. The sensor consists of a TEC (thermoelectric cooler) covered by a gold mirror. The TEC is controlled by a commercially available microprocessor with an on-board PID (proportional-integral-derivative) controller. The results of the CMH measurements are in good agreement with the industrial-made capacitive sensor. The absolute accuracy of the measured dew point temperature by the CMH is in the range of ±0.2 K. Spectra show evidence that the CMH is capable to measure turbulent humidity fluctuations in the atmosphere with a temporal resolution of up to 10 Hz. Such a fast humidity sensor aboard a small UAS has the potential to study humidity fluxes in the surface layer over complex terrain, behind wind energy converters and humidity variations over land and sea surfaces in general
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Case studies of the wind field around Ny-Ã…lesund, Svalbard, using unmanned aircraft
The wind field in Arctic fjords is strongly influenced by glaciers, local orography and the interaction between sea and land. Ny-Ã…lesund, an important location for atmospheric research in the Arctic, is located in Kongsfjorden, a fjord with a complex local wind field that influences measurements in Ny-Ã…lesund. Using wind measurements from UAS (unmanned aircraft systems), ground measurements, radiosonde and reanalysis data, characteristic processes that determine the wind field around Ny-Ã…lesund are identified and analysed. UAS measurements and ground measurements show, as did previous studies, a south-east flow along Kongsfjorden, dominating the wind conditions in Ny-Ã…lesund. The wind measured by the UAS in a valley 1 km west of Ny-Ã…lesund differs from the wind measured at the ground in Ny-Ã…lesund. In this valley, we identify a small-scale catabatic flow from the south to south-west as the cause for this difference. Case studies show a backing (counterclockwise rotation with increasing altitude) of the wind direction close to the ground. A katabatic flow is measured near the ground, with a horizontal wind speed up to 5 m s-1. Both the larger-scale south-east flow along the fjord and the local katabatic flows lead to a highly variable wind field, so ground measurements and weather models alone give an incomplete picture. The comparison of UAS measurements, ground measurements and weather conditions analysis using a synoptic model is used to show that the effects measured in the case studies play a role in the Ny-Ã…lesund wind field in spring