Infrasonic Observations of Some Atmospheric Phenomena Ludwik Liszka Swedish Institute of Space Physics, SE-901 87, Umeå, Sweden
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Infrasonic Observations of Some Atmospheric Phenomena
Ludwik Liszka
Swedish Institute of Space Physics, SE-901 87, Umeå, Sweden
The Swedish Infrasound Network
The Lidstrom-microphone
The Lidstrom-microphone: the frequency response
Wind noise reduction: wind barriers
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)
Infrasonic chirps
Time scale and dilation no.
Infrasonic chirps
Possible association with sprites
Cross-wind propagation
Case study on May 13, 2003: Jamton
Case study on May 13, 2003: Lycksele
Positions of events (x)
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.
Satellite image May 13, 2003 0914UT
Occurrence of chirps 1994-2004
Station Number of observed chirps
Kiruna None
Jamton 114
Lycksele 5
Uppsala 2
Azimuth distribution of chirps observed
in Jamton
Temporal distribution of chirps during 1994-2004
Solar activity (sunspot numbers) 1994-2004
Infrasonic signatures from thunderstorms
Thunderstorm cells on July 8, 2005 at 1424UT
High resolution analysis: angle-of-arrival and trace velocity
Geometry of the signal from a cloud-to-cloud discharge
High resolution analysis of a lightning
signature: azimuth
High resolution analysis of a lightning signature: trace velocity
Wavelet spectrum of the signature
High resolution analysis of a lightning signature: trace velocity vs azimuth
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
Thermistor masts
Temperature layers
Temperature waves
Temperature bursts
Horizontal extent: 75m separation
Dynamical properties
Dynamical properties
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
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
An unidentified ”sawtooth” signature
Conclusion
• An efficient tool to monitor processes resulting in a pressure transient/transients
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