Atmospheric infrasound from nonlinear wave interactions during Hurricanes Felicia and Neki of 2009

Monitoring stations around the globe routinely detect microbarom signals with a dominant frequency of similar to 0.2 Hz from regions of marine storminess. International Monitoring System (IMS) infrasound array IS59 in Kailua-Kona, Hawaii recorded clear signals in close proximity of Hurricanes Felicia and Neki of 2009 for a first-hand investigation of the detailed source mechanism through a hindcast analysis. A spectral wave model describes the tropical cyclone and ambient sea states through a system of two-way nested grids with forcing from a blended data set of global, regional, and cyclonic winds. The computed wave conditions are validated with altimetry measurements and utilized in an acoustic model to estimate the intensity and spatial distribution of the microbarom source. The model results elucidate origins of infrasound signals from the tropical cyclone waves as well as their interactions with the ambient conditions consisting of swells, wind seas, and storm waves from nearby systems. The positive correlation between the IS59 observations and the theoretical microbarom estimates, and the saturation of recorded signals from high-energy sources support the use of infrasound signals for inference of tropical cyclone waves. Citation: Stopa, J. E., K. F. Cheung, M. A. Garces, and N. Badger (2012), Atmospheric infrasound from nonlinear wave interactions during Hurricanes Felicia and Neki of 2009, J. Geophys. Res., 117, C12017, doi:10.1029/2012JC008257.