Open AccessAnalysis of the Spatial Coherence of Short‐Period Acoustic‐Gravity Waves in the Atmosphere
Author(s) -
Mack Harry,
Flinn Edward A.
Publication year - 1971
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1971.tb03399.x
Subject(s) - coherence (philosophical gambling strategy) , physics , phase velocity , wave propagation , gravity wave , atmosphere (unit) , coherence time , azimuth , transverse plane , acoustic wave , optics , phase (matter) , spatial coherence , internal wave , geology , acoustics , meteorology , structural engineering , engineering , quantum mechanics
Summary The coherence of atmospheric acoustic‐gravity waves has been measured in the period range 10–100 s at the Large Aperture Microbarograph Array in south‐eastern Montana. The acoustic‐gravity waves observed were signals generated by presumed nuclear explosions. The decrease of coherence with increasing distance between pairs of microbarographs is less rapid in the direction of wave propagation than transverse to it. Variation of direction of arrival over a small range of azimuth (±5°) explains the spatial behaviour of coherence in the direction normal to the wave propagation; variation of phase velocity of ±10 ms ‐1 explains the behaviour along the direction of wave propagation. Both effects may be due to inhomogeneities in the atmosphere; the velocity variation may be due to the presence in the signal of several normal modes of acoustic‐ gravity waves, each travelling at a slightly different phase velocity in the range 300–330 ms ‐1 .