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fs1.JPGJPEG image1559K(file fs01.jpg) presents the global stratospheric wind circulation on 15 February 2013 at 06:00 UTC, at 50 km altitude (ECMWF-91 profiles, 0.5°x0.5° resolution, 91 altitude levels, http://www.ecmwf.int/). Background color indicates the wind speed (in m/s) and black arrows wind direction and strength. Blue triangles indicate IMS stations. Stations where infrasound signals were detected appear in filled blue colored triangles. The white star shows the location of the main blast of the fireball.
fs2.jpgJPEG image476K(file f2.jpg) presents the global picture of the travel-times for Ig1 (top) and Ig2 (bottom) calculated in each direction from the source. The effective sound speed ratio along each great-circle path is color coded: white (Veff-ratio >1: downwind situation with favorable stratospheric ducting), grey: Veff-ratio between 0.97 and 1 (stratospheric returns are likely due to diffraction effects and small-scale structures not resolved by the atmospheric model), black: Veff-ratio<0.97 (upwind situation with likely thermospheric ducting).
fs3.jpgJPEG image382K(file fs3.jpg) presents propagation paths from the main blast of the fireball at 25 km altitude. Range-dependent atmospheric specifications are given by the ECMWF-91 model on 15 February 2013 at 06:00 UTC. The variation of the maximum of the effective sound speed between 30 and 60 km altitude is color coded. Values larger than the sound speed at the ground level (warm color) indicate altitudes of minimum ray turning height. The blast source is indicated by the black star and the receiving stations by black triangles. A: ray paths towards IS21 (Marquises Island) for Ig1 (to the right) and Ig2 (to the left). B: ray paths towards IS27 (Antarctica) for Ig1 (to the right) and Ig2 (to the left). C: ray paths towards IS26 (Germany) for Ig1 and Ig3.
ts1.docxWord 2007 document24K(file ts1.docx) details the main characteristics of infrasound waves from the fireball recorded at 20 IMS stations. Stations are sorted by distance. Signals have been processed using 20 log-spaced frequency bands from 0.01 and 4 Hz. Maximum peak-to-peak amplitude is determined by band-passing the stacked channel (0.02-1 Hz) using a second-order Butterworth filter. Dominant periods are tabulated by taking an inverse of the frequency at the maximum power spectral density (PSD) of the entire signal, 0.02-1 Hz band-pass filtered and stacked along the array beam. Ig1 and Ig2 denote the minor and major arcs of the great circle path, respectively. Ig3 and Ig5 respectively denote the minor arc of the great circle path with one and two complete revolutions around the globe. Celerity is calculated considering the onset time of the detected waveforms referring to an origin time of 03:20:26 UTC on Feb. 15 and a point-like source at 54.8°N 61.1°E. The maximum of the effective sound speed ratio (Veff-ratio) between 30 and 60 km altitude averaged along each propagation path is indicated for Ig1 and Ig2. Arrivals Igx* refer to thermospheric returns.
readme.docxWord 2007 document17KSupporting Information

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