  The receiver-to-source backazimuth of atmospheric infrasound signals is
biased when cross-winds are present along the propagation path. Infrasound from
598 surface explosions from over 30 years in northern Finland is measured with
high spatial resolution on an array 178 km almost due North. The array is
situated in the classical shadow-zone distance from the explosions. However,
strong infrasound is almost always observed, which is most plausibly due to
partial reflections from stratospheric altitudes. The most probable propagation
paths are subject to both tropospheric and stratospheric cross-winds, and our
wave-propagation modelling yields good correspondence between the observed
backazimuth deviation and cross-winds from the ERA-Interim reanalysis product.
We demonstrate that atmospheric cross-winds can be estimated directly from
infrasound data using propagation time and backazimuth deviation observations.
We find these cross-wind estimates to be in good agreement with the ERA-Interim
reanalysis.
