Evaluating the opposing-wave interaction hypothesis for the generation of microbaroms in the eastern North Pacific

Two microphone arrays were deployed in California during 2010 to record microbaroms, quasi-continuous atmospheric pressure oscillations with a period of ~5 s. Here I present a time-progressive, frequency-domain beamforming method and analyze microbaroms recorded from November 2010 through December 2011 by these and ten other infrasonic arrays along the North Pacific rim. Common pelagic microbarom sources that move around the north Pacific are observed during the boreal winter. Summertime microbarom sources are only observed by western Pacific arrays, presumably a result of weaker microbarom radiation and westward stratospheric winds. A well-defined source is resolved ~2000 km off the coast of California in January 2011 that moves closer to land over several days. This source location is corrected for deflection by horizontal winds using acoustic ray-trace modeling with range-dependent atmospheric specifications provided by ground-to-space (G2S) models. The source locations do not correlate with anomalies in NOAA Wave Watch 3 (NWW3) model field data. However, I apply the opposing-wave, microbarom source model of Waxler and Gilbert (2006) to the NWW3 directional wave height spectra output at buoy locations within ~1000 km of the western North America coastline and show that the spatial locations of the predicted microbarom source correlate well with the location of the observed microbaroms ~500 km off the coast. These results suggest that pelagic North Pacific microbarom radiation detected by infrasonic arrays during the boreal winter could be routinely used to validate NWW3 results in regions with poor sensor coverage.