Switch on tunnel vision: Portable wind tunnels to understand and quantify aeolian processes

A Portable wind tunnel is a highly specialized device capable of examining soil surfaces in their natural state and independently from naturally occurring wind events. The field experiments give valuable insights into wind-induced entrainment, transport, redistribution and emission of mineral and organic particles from surfaces in their original state to understand geomorphological, pedological, and ecological processes. Recent portable wind tunnel studies highlight a broad range of research objectives including the determination of threshold wind velocities, the quantification of wind-eroded sediment, the development of dust emissions, and wind-induced dynamics of nutrients and contaminants. Portable wind tunnels usually follow a straight tunnel design with a push or suction-type wind source, an air straightening section, and an open-bottom test area. Research groups developed and applied specific add-on features such as sediment feeders to simulate an erosive saltation layer, an integrated rainfall simulator for wind-driven rain studies, and miniaturized tunnels. A large variety of techniques is used to collect and count the entrained mineral and organic particles to allow for quantification and qualitative analysis. Validity, reproducibility, and reliability of the experimental setup and data application for extrapolation and modeling are discussed based on physical constraints of the tunnel and spatio-temporal characteristics of the data. The manuscript also summarizes experiences and recommendations for application and maintenance and proposes methods to compare results generated by different devices.