Analysis of airborne measurements from paragliders to detect thermal structures in the mountain atmospheric boundary layer

A field campaign was conducted during September 2019 on Monte Avena, south-eastern Italian Alps, to assess the feasibility and quality of an innovative measurement technique for the study of thermal structures in the atmospheric boundary layer over mountains. Paragliders were equipped with non-conventional instruments for airborne measurements of meteorological variables, such as air temperature, relative humidity, atmospheric pressure, and wind intensity and direction. The work aims at testing to what extent the instrumented paraglider can represent a valid method for acquiring physical information on thermal structures. The paraglider presents a combination of properties that make it extremely useful for the detection of thermals, compared to other flying vehicles adopted for airborne measurements such as aeroplanes and gliders. A new method for identifying thermals, based on the engine-free property of the paraglider, is proposed and the results suggest its reliability. Measurements have been analysed by means of vertical profiles and horizontal and vertical maps of temperature, virtual potential temperature, water vapour mixing ratio and vertical wind speed. Agreement was found between in-flight measurements and data from soundings and local surface weather stations. Even though the adopted instruments have shown several issues in measuring the atmospheric variables, the new method of collecting atmospheric data by means of an instrumented paraglider has turned out to be promising, both for the identification and characterisation of thermal structures in the mountain boundary layer, and for the study of the basic state of the atmosphere.