Lighter-than-air particle velocimetry for wind speed profile measurement

The objective of this paper is to consolidate the backgrounds of a method to measure the local wind speed profiles by remotely tracking lighter-than-air bubble clusters, in a way that is efficient, safe and easily implementable. The technologies around remote sensing of atmospheric wind profiles are reviewed, together with those associated with particle image velocimetry. In this case, the targets are light liquid bubbles filled with helium, which are monitored from several locations on ground so that the full trajectory can be reproduced and hence, the wind speed derived at each point along the path. The features of the measurement system are detailed, describing its major components. The different applicable data filtering processes, the core of the operation, are reviewed to find the best options for the estimation of the wind profile in real time. The capability to measure the horizontal wind along the ascending path of the targets has been checked by means of simulated scenarios, indoor campaigns and in-field tests. The synthetic scenarios allowed the tuning of photometric parameters as well as the first estimation of the performance and the limitations. The field test campaigns allowed validating the prototype under different configurations and atmospheric conditions. Initial tests were conducted in a Spanish atmosphere research centre (CIBA), where wind data until 100 m height is continuously recorded, followed by additional experiments in a more realistic environment, near an airport, where these data could be operationally used in the future. The results from these tests are successful, taking into account the fact that the system is still in an early development phase, while still being able to beat initial performance goals (0.4 m/s mean error for wind speed and 15° for wind direction). It is expected that the idea is a reliable and low cost alternative to other remote sensing devices for wind profile measurement in certain applications in the medium-accuracy range.