T1-O1 Infrasound - from explosion monitoring to atmospheric studies

Comprehensive Nuclear-Test-Ban Treaty (CTBT): Science and Technology 2011Vienna, Austria, 8-10 June 2011

Infrasound: From explosion monitoring

to atmospheric studies and climate

Elisabeth BlancCEA DAM DIF F-91297 Arpajon France

[email protected]


• 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

Outline


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


Atmospheric disturbances observed by the infrasound networkInfrasound waves: frequencies 10 Hz to ~0.03 Hz measured with an unprecedented accuracy, motivating new atmospheric research: Rebirth of infrasound science

Elastic wavesPropagation at the sound velocity

Buoyancy waves Propagation velocity < sound velocityWavelength : tens to thousands kilometers, very large amplitude

Sources: explosions, volcanoes, earthquakes, lightning, auroras, ocean swell, thunderstorms, wind over mountains, meteorites…etc


Large scale waves: Gravity waves: periods from 5 minutes up to several hours, atmospheric tides, planetary wavesSources: Thunderstorms, Convection, Wind over mountains

Universal spectrum of atmospheric waves

Marty, 2010

Atmospheric disturbances observed by the infrasound network


Stratospheric winds

ThermosphereThermosphere

Stratosphere

Infrasound propagation in the atmospheric wave guide

Propagation in the atmospheric wave guide, formed by the temperature and wind variations in the different atmospheric layers.

Acoustic ray tracing

Wind velocity (m/s)

Temperature (°K)

Shadow zone


Infrasound propagation in the atmospheric wave guide

Propagation in the atmospheric wave guide, formed by the temperature and wind variations in the different atmospheric layers.

Infrasound propagation in Central Europe during summerwest east

Parabolic model including acoustic spreading and attenuation

Ceranna, ISS 2009


The Buncefield explosion

HWM-93

simulation observation

Ceranna et al., GJI, 2009

Large explosion at the Buncefield Oil Depot, United Kingdom, on the 2005 December 11, ~ 300 tonnes of petrol


Ceranna et al., GJI, 2009

The Buncefield explosion

NRL-G2S

simulation observation

Large explosion at the Buncefield Oil Depot, United Kingdom, on the 2005 December 11, ~ 300 tonnes of petrol


The dense seismic USArray, composed of 70-km spaced 400-station, fills in the gaps between infrasonic arrays.

Synergy between infrasound and seismology

0.8 – 3.0 Hz bandpass

Infrasound source: rocket motor detonations at the UTTR facility in Utah

The observed shadow zones have considerably narrower spatial extent than simulations predict, perhaps due to un-modeled small-scale structure in the atmosphere.

Hedlin et al. , EGU201 1


Standard mean profile

Partial reflections from small scale structures

Distance (km)

Effects of small-scale atmospheric structures

It

It

Is

Ceff (m/s)

Small scale structures are mainly produced by gravity waves. The partial reflection coefficient is larger in Summer

Kulichkov et al., 2010, ITW 2010, Kulichkov et al., Infrasound book, Springer, 2010

MST radar

Infrasound from explosions


Improved empirical attenuation law

P = 101.5745 + 0.018•Vs • R-1.4072 • Y0.7036P : pressure (Pa), E : yield (t), R : distance (km), Vs : stratospheric wind speed

Whitaker, 1995

Distance (km)

Whitaker relation

Atte

nuat

ion

(dB

)

150

100

50

0

Down-wind

Up-wind


Improved empirical attenuation laws

Prec/ Psoc = R-1 • 10 (α•R)/20 + Rβ / (1+10(δ-R)/σ)

α : air losses of direct wavesβ : geometrical spreading of ducted wavesδ : width of shadow zoneσ : std deviation of shadow zone’s width

Ceranna et al., EGU 2011Le Pichon et al, JGR,submitted

The empirical attenuation law has been improved by using propagation models and including realistic atmospheric parameters

Distance (km)

Whitaker relation

Atte

nuat

ion

(dB

)

150

100

50

0

Down-wind

Up-wind

Shadow zone


Improved empirical attenuation laws

The presence of atmospheric irregularities or gravity waves increases thedetection capabilities

Distance (km)

Whitaker relation

Atte

nuat

ion

(dB

)

150

100

50

0

Ceranna et al., EGU 2011Le Pichon et al, JGR,submitted

0 Shadow zone with GW

no GW


Improved detection capabilities maps

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


Calibration experimentSayarim January 25, 2011

Detection at I31KZ - 2990 km

Detection at I34MN - 6300 km

Detection at I46RU - 4790 km

No detection

Detection

Strong support from the University of Mississippi, Weston Geophysical, Israel NDC, Geophysical Institute of Israel

20 countries participated in observations

The CTBTO team deployed 18 portable infrasound arrays,and coordinated deployment.

Le Pichon et al, 2011


Eyjafjallajökull eruption

Matoza et al, GRL, 2011Ripepe et al., 2011

Explosive phase in April 2010


Assink et al., submitted to JGR, 2011

Azimuth deviation amplitude (~5°) underestimated by the models

Deviation <1°

Deviation ~5°

Green et al., ITW 2010, Tunisia

Signature of atmospheric tides in volcano signals

Model

Data

Tungurahua, May, june 2010 Eyjafjallajökull, April 2010

Interdiurnal variation not captured in G2S/HWM. Errors in traveltime ~ 10%


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

Iyer A. S., F. M. Ham, and M. A. Garces (2011). Neural Classification of Infrasonic Signals Associated with Hazardous Volcanic Eruptions, International Joint Conference on Neural Networks, San Jose, CA.

Garces et al, 2011


New challenge : Infrasound for remote sensing of the atmosphere

Le Pichon et al. , 2005a, b

Original wind model

0

50

100

Altit

ude

(km

) Wind speed

(m/s)

-50

0

50Corrected wind model

Such observations are proposed to improve atmospheric models


New challenge : Infrasound for remote sensing of the atmosphere

Le Pichon et al. , 2005a, b

Such observations are proposed to improve atmospheric models

Wind speed

(m/s)

-60

-20

-40

0

-80

60

80

100

120

Altit

ude

(km

)

Original wind model

Local time (hours)

40

Corrected wind model


(a) True wind profiles (solid lines) and inital wind profiles (dashed lines). (b-d) Reconstructed profiles from inversion using 150 to 10 infrasound arrays

Atmospheric remote sensing: new challenge

Lalande et al., submitted JGR, 2011

Up to 10 stations are needed to fully reconstruct the wind profile

Zonal windMeridionalwind


Infrasound from sprites: direct detection and localisation

Location of the infrasound source inside the sprite structure: from measurements of arrival direction, elevation angle and from parent lightning position

EUROSPRITE campaigns

Farges and Blanc, JGR, 2010


Jan 2007 Jul Apr Oct

IS17

May

August

November

Jan Jul

General circulation from East

InterTropicalConvergence Zone (ITCZ)

Jan Jul

General circulation from East

InterTropicalConvergence Zone (ITCZ)

The very intense gravity wave activity in West Africa originates from thundersormsBlanc et al, AGU 2009

Large source of atmospheric waves: African thunderstormsLarge scale gravity waves (period from 8 min to several hours) ⇒ impact on the environment


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 of gravity waves in amospheric models will improve short and medium range weather forecast and climate models. 25/13

Climate change and wave activity


- Infrasound: CTBT network and national networks- Mesosphere: NDMC (Network for the Detection of Mesopause Changes) Optical observations of the mesospheric night airglow layer

IS31IS43

IS18

IS26

IS42

IS48

IS37

IS31IS43

IS18

IS26

IS42

IS48

IS37

CTBTstationsNational stationsNDMC stationsNDACC stations

IS31IS43

IS18

IS26

IS42

IS48

IS37

IS31IS43

IS18

IS26

IS42

IS48

IS37

IS31IS43

IS18

IS26

IS42

IS48

IS37

CTBTstationsNational stationsNDMC stationsNDACC stations

- Stratosphere: NDACC (Network for the Detection of Atmospheric Composition Changes) Lidar observations of the stratosphere and mesosphere - Satellites: SABER …

ARISE Atmospheric dynamics Research InfraStructure in Europe

-Consortium members:France (CEA : leader du projet, LATMOS) Germany (BGR+DLR), Italy (Univ. Florence), Netherlands (KNMI), Norway (NORSAR), United Kingdom (Univ. Reading), Sweden (IRF), Czech Republic (IAP), Belgium (BISA)- Associated members: AT,GB, IS, DK, RO, PT, RU, KZ, TN, MG, CI …

Design Study project - Infrastructure program – Start January 2011

- 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

Control stations


Project objectives

ARISE covers three important topics related to•"natural and human-induced disasters", •"understanding, predicting, climate" •"Improving weather forecasting"

which are included in the nine societal benefit areas listed in the GEOSS 10-Year Implementation Plan

ARISE project, 2011


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»

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

2011 achievementsEffects 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

In return….Improvement of the knowledge of the atmosphere from infrasound observations will strength the infrasound processing methods by:- increasing the location precision - improving estimates of detection capabilities - better identification of noise and other disturbances of Earth environment

Conclusion

T1-O1 Infrasound - from explosion monitoring to atmospheric studies

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