Three-Dimensional Temperature and Wind Profiles Obtained Using UAV-Based
Acoustic Atmospheric Tomography
Abstract
The natural sound generated by an unmanned aerial vehicle is used in
conjunction with tomography to remotely sense atmospheric temperature
and wind profiles simultaneously. Sound fields recorded onboard the
aircraft and by an array of microphones on the ground are compared and
converted to sound speed estimates for the ray paths intersecting the
intervening medium. Tomographic inversion is then used to transform
these sound speed values into vertical cross-sections and 3D volumes of
virtual temperature and wind vectors, which enables the atmosphere to be
visualised and monitored over time up to altitudes of 1,200m and over
baselines of up to 600m. This paper reports on results from two short
campaigns during which 2D and 3D profiles of wind and temperature
obtained in this way were compared to: measurements taken by co-located
mid-range Doppler SODAR and LIDAR; and temperature measurements made by
instruments carried by unmanned aircraft flying through the intervening
atmosphere. Large eddy simulation of daytime atmospheric boundary layers
were also used to examine the anticipated performance of the instruments
and the nature of any errors. The observations obtained using all
systems are shown to correspond closely.