Infrasound: From explosion monitoring to atmospheric studies and climate

Transcription

1 Infrasound: From explosion monitoring to atmospheric studies and climate Elisabeth Blanc CEA DAM DIF F Arpajon France

2 Outline Monitoring of infrasound from explosive sources Detection capability Monitoring of infrasound from volcanoes Monitoring of infrasound from thunderstorms Interest of the infrasound observations for weather forecasting and climate Conclusions

3 The IMS infrasound network 60 infrasound stations providing permanent, homogeneous global observations of all atmospheric disturbances Currently 43 stations are installed and 70 % are certified Stations are very sensitive acoustic antennas measuring wave parameters in a broad frequency range Grenard, ITW, 2010

4 Atmospheric disturbances observed by the infrasound network Infrasound waves: frequencies 10 Hz to ~0.03 Hz measured with an unprecedented accuracy, motivating new atmospheric research: Rebirth of infrasound science Sources: explosions, volcanoes, earthquakes, lightning, auroras, ocean swell, thunderstorms, wind over mountains, meteorites etc Buoyancy waves Propagation velocity < sound velocity Wavelength : tens to thousands kilometers, very large amplitude Elastic waves Propagation at the sound velocity

5 Atmospheric disturbances observed by the infrasound network Large scale waves: Gravity waves: periods from 5 minutes up to several hours, atmospheric tides, planetary waves Sources: Thunderstorms, Convection, Wind over mountains Marty, 2010 Universal spectrum of atmospheric waves

6 Infrasound propagation in the atmospheric wave guide Temperature ( K) Acoustic ray tracing Thermosphere Thermosphere Stratospheric winds Shadow zone Stratosphere Wind velocity (m/s) Propagation in the atmospheric wave guide, formed by the temperature and wind variations in the different atmospheric layers.

7 Infrasound propagation in the atmospheric wave guide Parabolic model including acoustic spreading and attenuation Infrasound propagation in Central Europe during summer west east Propagation in the atmospheric wave guide, formed by the temperature and wind variations in the different atmospheric layers. Ceranna, ISS 2009

8 The Buncefield explosion Large explosion at the Buncefield Oil Depot, United Kingdom, on the 2005 December 11, ~ 300 tonnes of petrol simulation observation Ceranna et al., GJI, 2009 HWM-93

9 The Buncefield explosion Large explosion at the Buncefield Oil Depot, United Kingdom, on the 2005 December 11, ~ 300 tonnes of petrol simulation observation Ceranna et al., GJI, 2009 NRL-G2S

10 Synergy between infrasound and seismology The dense seismic USArray, composed of 70-km spaced 400-station, fills in the gaps between infrasonic arrays. The observed shadow zones have considerably narrower spatial extent than simulations predict, perhaps due to un-modeled small-scale structure in the atmosphere Hz bandpass Hedlin et al., EGU201 1 Infrasound source: rocket motor detonations at the UTTR facility in Utah

11 Effects of small-scale atmospheric structures Standard mean profile It Small scale structures are mainly produced by gravity waves. The partial reflection coefficient is larger in Summer Infrasound from explosions Partial reflections from small scale structures It MST radar Is Ceff (m/s) Distance (km) Kulichkov et al., 2010, ITW 2010, Kulichkov et al., Infrasound book, Springer, 2010

12 Improved empirical attenuation law Attenuation (db) 0 50 Whitaker relation Down-wind Up-wind Distance (km) P = Vs R Y P : pressure (Pa), E : yield (t), R : distance (km), Vs : stratospheric wind speed Whitaker, 1995

13 Improved empirical attenuation laws Attenuation (db) Whitaker relation Shadow zone Down-wind Up-wind Distance (km) Prec/ Psoc = R-1 10 (α R)/20 + Rβ / (1+10(δ-R)/σ) α : air losses of direct waves β : geometrical spreading of ducted waves δ : width of shadow zone σ : std deviation of shadow zone s width Ceranna et al., EGU 2011 Le Pichon et al, JGR,submitted The empirical attenuation law has been improved by using propagation models and including realistic atmospheric parameters

14 Improved empirical attenuation laws Attenuation (db) Whitaker relation Shadow zone with GW no GW Distance (km) The presence of atmospheric irregularities or gravity waves increases the detection capabilities Ceranna et al., EGU 2011 Le Pichon et al, JGR,submitted

15 Improved detection capabilities maps Le Pichon et al., submitted JGR 2011 The new attenuation laws are used to predict the detection conditions at local or global scale

16 Calibration experiment Sayarim January 25, 2011 Detection at I31KZ km 20 countries participated in observations Detection at I46RU km Detection at I34MN km No detection Detection Le Pichon et al, 2011 The CTBTO team deployed 18 portable infrasound arrays, and coordinated deployment. Strong support from the University of Mississippi, Weston Geophysical, Israel NDC, Geophysical Institute of Israel

17 Eyjafjallajökull eruption Explosive phase in April 2010 Matoza et al, GRL, 2011 Ripepe et al., 2011

18 Signature of atmospheric tides in volcano signals Interdiurnal variation not captured in G2S/HWM. Errors in traveltime ~ 10% Azimuth deviation amplitude (~5 ) underestimated by the models Deviation ~5 Data Model Deviation <1 Tungurahua, May, june 2010 Eyjafjallajökull, April 2010 Assink et al., submitted to JGR, 2011 Green et al., ITW 2010, Tunisia

19 Garces et al, 2011 Acoustic Surveillance for Hazardous Eruptions (ASHE) Identified Infrasonic Fingerprint of a Plinian Eruption at Tungurahua, Ecuador ID hazardous eruptions Train neural net Extend to IRED Extend to IMS Implement in real time Comprehensive Iyer A. S., F. Nuclear-Test-Ban M. Ham, and M. A. Garces Treaty (2011). (CTBT): Neural Science Classification and Technology of Infrasonic Signals 2011Associated with Hazardous Volcanic Vienna, Eruptions, Austria, International 8-10 June Joint Conference 2011 on Neural Networks, San Jose, CA.

20 New challenge : Infrasound for remote sensing of the atmosphere Altitude (km) Original Corrected wind wind model model Wind speed (m/s) 0 Le Pichon et al., 2005a, b Such observations are proposed to improve atmospheric models

21 New challenge : Infrasound for remote sensing of the atmosphere Altitude (km) Original Corrected wind wind model model Wind speed (m/s) Local time (hours) Le Pichon et al., 2005a, b Such observations are proposed to improve atmospheric models

22 Atmospheric remote sensing: new challenge Zonal wind Meridional wind (a) True wind profiles (solid lines) and inital wind profiles (dashed lines). (b-d) Reconstructed profiles from inversion using 150 to 10 infrasound arrays Up to 10 stations are needed to fully reconstruct the wind profile Lalande et al., submitted JGR, 2011

23 Infrasound from sprites: direct detection and localisation Farges and Blanc, JGR, 2010 Location of the infrasound source inside the sprite structure: from measurements of arrival direction, elevation angle and Comprehensive EUROSPRITE campaigns Nuclear-Test-Ban Treaty (CTBT): Science and Technology 2011 Vienna, from parent Austria, lightning 8-10 June position 2011

24 Large source of atmospheric waves: African thunderstorms Large scale gravity waves (period from 8 min to several hours) impact on the environment August IS17 November May InterTropical Convergence Zone (ITCZ) Jan Jul Jan 2007 Apr Jul Oct General circulation from East Blanc et al, AGU 2009 The very intense gravity wave activity in West Africa originates from thundersorms

25 Climate change and wave activity Forcing of the stratosphere and mesosphere by atmospheric waves - Long-lived changes in the stratospheric circulation Memory of the stratosphere - Fluctuations in the polar vortex (Sudden Stratospheric Warming) - Possible effects on the troposphere and climate Changes in the number of severe thunderstorms and hurricanes? - Possible decrease in the globally averaged frequency of severe thunderstorms and cyclones - But increase in the frequency of the most intense of them Conflicting results because of differences in the different regions of the Earth and lack of observing capabilities Operational observations of gravity waves are still limited. It is proposed to measure gravity/planetary wave permanently and at global scale for model improvement. Assimilation Comprehensive of gravity Nuclear-Test-Ban waves in amospheric Treaty models (CTBT): will Science improve and short Technology and medium 2011 range weather forecast and climate models. 25/13

26 ARISE Atmospheric dynamics Research InfraStructure in Europe Design Study project - Infrastructure program Start January 2011 IS18 IS37 IS37 CTBTstations National stations NDMC stations NDACC stations IS43 IS31 IS31 IS26 IS26 IS42 IS48 - Infrasound: CTBT network and national networks - Mesosphere: NDMC (Network for the Detection of Mesopause Changes) Optical observations of the mesospheric night airglow layer - Stratosphere: NDACC (Network for the Detection of Atmospheric Composition Changes) Lidar observations of the stratosphere and mesosphere - Satellites: SABER Control stations - Volcanic sources: infrasound stations in Iceland, Stromboly, Etna - Tropical gravity wave sources (Thunderstorms) : CTBT infrasound African stations, Reunion Island lidar station - High altitude ionospheric coupling : CZ ionospheric/infrasound station -Consortium members: France (CEA : leader du projet, LATMOS) Germany (BGR+DLR), Italy (Univ. Florence), Netherlands (KNMI), Norway (NORSAR), United Comprehensive Kingdom (Univ. Reading), Nuclear-Test-Ban Sweden (IRF), Treaty Czech (CTBT): Republic Science (IAP), and Belgium Technology (BISA) Associated members: AT,GB, Vienna, IS, DK, Austria, RO, PT, 8-10 RU, June KZ, TN, 2011 MG, CI

27 Project objectives ARISE covers three important topics related to "natural and human-induced disasters", ARISE project, 2011 "understanding, predicting, climate" Comprehensive "Improving Nuclear-Test-Ban weather forecasting" Treaty (CTBT): Science and Technology 2011 which are included in the nine Vienna, societal benefit Austria, areas 8-10 listed June in the 2011 GEOSS 10-Year Implementation Plan

28 Conclusion Pionner work of Rind et al, 1973 «We suggest that use of an expanded "synoptic" network of infrasound recorders would provide a simple procedure to monitor conditions in the upper atmosphere» 2011 achievements Effects of the atmosphere well integrated in the infrasound propagation models Possibility of predicting propagation with a precision depending on the precision of the atmospheric models Remote sensing by using infrasound can be used to measure atmospheric parameters Next challenges The infrasound network is more and more essential for civil applications as volcanic monitoring (aviation safety) It will also becomes very quickly essential for studies of large scale waves and atmospheric dynamics for improving weather forecasting and climate studies In return. Improvement of the knowledge of the atmosphere from infrasound observations will strength the infrasound processing methods by: - increasing the location precision - improving Comprehensive estimates of Nuclear-Test-Ban detection capabilities Treaty (CTBT): Science and Technology better identification of noise and Vienna, other Austria, disturbances 8-10 June of Earth 2011 environment