1. Infrasonic Observations of Some Atmospheric Phenomena Ludwik Liszka Swedish Institute of Space Physics, SE-901 87, Umeå, Sweden

2. The Swedish Infrasound Network

3. The Lidstrom-microphone

4. The Lidstrom-microphone: the frequency response

5. Wind noise reduction: wind barriers

6. 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)

7. Infrasonic chirps

8. Time scale and dilation no.

9. Infrasonic chirps

10. Possible association with sprites

11. Cross-wind propagation

12. Case study on May 13, 2003: Jamton

13. Case study on May 13, 2003: Lycksele

14. Positions of events (x)

15. 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.

16. Satellite image May 13, 2003 0914UT

17. Occurrence of chirps 1994-2004 StationNumber of observed chirps Kiruna None Jamton114 Lycksele5 Uppsala2

18. Azimuth distribution of chirps observed in Jamton

19. Temporal distribution of chirps during 1994-2004

20. Solar activity (sunspot numbers) 1994-2004

21. Infrasonic signatures from thunderstorms

22. Thunderstorm cells on July 8, 2005 at 1424UT

23. High resolution analysis: angle-of-arrival and trace velocity

24. Geometry of the signal from a cloud-to- cloud discharge

25. High resolution analysis of a lightning signature: azimuth

26. High resolution analysis of a lightning signature: trace velocity

27. Wavelet spectrum of the signature

28. High resolution analysis of a lightning signature: trace velocity vs azimuth

29. Trace velocity and the temperature Elevation: E=cos -1 (C/ V p ). where C is the speed of sound and Vp is the trace velocity. C = 20.75  T where T is the temperature in degrees Kelvin

30. Thermistor masts

31. Temperature layers

32. Temperature waves

33. Temperature bursts

34. Horizontal extent: 75m separation

35. Dynamical properties

37. 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/abstract s/256abs.php

38. An unidentified ”sawtooth” signature

39. Characterized by very high trace velocities Most likely not connected with human activities (a natural phenomenon) Indications of correlation across considerable distances

40. An unidentified ”sawtooth” signature

41. Conclusion An efficient tool to monitor processes resulting in a pressure transient/transients