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Infrasonic Observations of Some Atmospheric Phenomena
Ludwik Liszka
Swedish Institute of Space Physics, SE-901 87, Umeå, Sweden
Selection of the frequency window
• The choice of frequency range for the network was based on the discovery of the ”optimum detection window” around 2 Hz by Procunier & Sharp (1970)
Background noise during the events
Lycksele shows on that particular date the lowest amplitude of the uncorrelated background of all SIN stations, only 0.014 Pa (peak value). At Jämtön the corresponding amplitude is 0.045 Pa.
Occurrence of chirps 1994-2004
Station Number of observed chirps
Kiruna None
Jamton 114
Lycksele 5
Uppsala 2
Trace velocity and the temperature
Elevation:
E=cos-1(C/ Vp).
where C is the speed of sound and Vp is the trace velocity.
C = 20.75T
where T is the temperature in degrees Kelvin
Summer atmosphere: thunderstorm related temperature waves
Thermistor Measurements of Temperature Oscillations During the Arctic Summer: Potential Coupling Between Severe Convective Thunderstorms and the Surface Prandtl Layer
A report by Ludwik Liszka and Douglas ReVelle at:
http://www.umea.irf.se/ume/publications/abstracts/256abs.php
An unidentified ”sawtooth” signature
• Characterized by very high trace velocities
• Most likely not connected with human activities (a natural phenomenon)
• Indications of correlation across considerable distances
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