FIGURE 4

Lower (a): 48 hr pressure trace showing “spike” referred to in text recorded at 4 p.m. Local Standard Time or 2100 GMT, 28 January 1977 in Ithaca, New York. Pressure range of 0.5 inch corresponds to -16 mb in SI units.
Middle (b): Pressure trace at same location showing “sawtooth” pattern mentioned in text (spanning 4 p.m. LST, or 2100 GMT). Pressure range of ~ 0.18 inch corresponds to 6 mb.
Upper (c): Acoustic-gravity wave trace recorded at same location, showing high amplitude infrasound trace spanning period from 2055 to 2107 GMT, 28 January 1977. Dotted completion of pressure peaks was necessitated where pen encountered edge of chart during the period of rapid pressure rise. (Trace courtesy Cornell's Neurobiological Behavior Laboratory.)