title: A wide-angle high Mach number modal expansion for infrasound propagation.
abstract: The use of modal expansions to solve the problem of atmospheric infrasound propagation is revisited. A different form of the associated modal equation is introduced, valid for wide-angle propagation in atmospheres with high Mach number flow. The modal equation can be formulated as a quadratic eigenvalue problem for which there are simple and efficient numerical implementations. A perturbation expansion for the treatment of attenuation, valid for stratified media with background flow, is derived as well. Comparisons are carried out between the proposed algorithm and a modal algorithm assuming an effective sound speed, including a real data case study. The comparisons show that the effective sound speed approximation overestimates the effect of horizontal wind on sound propagation, leading to errors in traveltime, propagation path, trace velocity, and absorption. The error is found to be dependent on propagation angle and Mach number.
authors.affiliation: R&D Department of Seismology and Acoustics, Royal Netherlands Meteorological Institute (KNMI) P.O. Box 201, 3730 AE, De Bilt, The Netherlands.
authors.forename: Jelle
authors.initials: J
authors.lastname: Assink
authors.affiliation: National Center for Physical Acoustics, University of Mississippi, P.O. Box 1848, University, Mississippi 38677, USA.
authors.forename: Roger
authors.initials: R
authors.lastname: Waxler
authors.affiliation: Leidos Corporation, 14668 Lee Road, Chantilly, Virginia 20151, USA.
authors.forename: Doru
authors.initials: D
authors.lastname: Velea