The Temporal Morphology of Infrasound Propagation
Douglas P. Drob1, Milton Garces2, Michael Hedlin3, and Nicolas Brachet4
1)Space Science Division, Naval Research Laboratory, Washington, DC2)Infrasound Laboratory, University of Hawaii, Kona3)Laboratory for Atmospheric Acoustics, University of California, San Diego4)International Data Center, Provisional Technical Secretariat, CTBTO, Vienna Austria
Why are precomputed monthly average travel time tables poor for operational infrasound source location calculations?
Expert knowledge suggests that the performance of automated infrasound event association and source location algorithms will be greatly improved by the ability to continual update station travel time curves to properly account for the seasonal/daily/hourly changes of the atmospheric state.
- thus -
Advocate for, develop, and integrate this capability into automated source location operations to reduced false alarm rates and improved network detection capability.
Requirements• Knowledge of the atmospheric state.• Procedures for calculating infrasound
propagation characteristics.• Procedures for utilization of travel time curves
in automated event association and location algorithms.
• Validation.• Systems integration.
Knowledge of the Atmospheric State
• HWM-93– empirical climatology– data sparse– low resolution– global– time dependent– 0 to 500 km
• Numerical weather prediction– operational– data rich– high-resolution– global/regional– 4x daily– 0 to 55/85 kmNOAA-GSF, ECMWF, NASA-GEOS5,
NOGAPS.
• Hybrid Ground-to-Space Model
• Seamless global specification - U, V, T, and P.
• Operational prototype, 4x daily from September 2002 to current, plus specific events to 1990.
Meridional Wind(N-S)
Zonal Wind (E-W)
Static Sound Speed
Methodology• 4x daily empirical climatologic and G2S
atmospheric specifications from September 13, 2002 to April 31, 2007.
• Tau-P infrasound propagation characteristics (Garces et al., 1998).
• Calculate celerity, azimuth deviation, and turning height for all azimuths up to 35° elevation.
• Calculated from the network receiver perspective.
I56US Mid-latitude
January 1, 2006 0:00 UT
260 280 300 320 340 3600
20
40
60
80
100
120
-100 -50 0 50 1000
20
40
60
80
100
120
Sound Velocity (m/s) Wind Velocity (m/s)
Altit
ude
(km
)Zonal Meridional
Phase Velocity (m/s)
Back Azimuth (from receiver)
Ele
vatio
n
-150 -100 -50 0 50 100 1500
5
10
15
20
25
30
330
340
350
360
370
380
390
400
Effective Sound Velocity (m/s)
Back Azimuth (Deg)
Alti
tude
(km
)
-150 -100 -50 0 50 100 1500
20
40
60
80
100
120
250
300
350
400
Turning Height (km)
Back Azimuth
Ele
vatio
n
-150 -100 -50 0 50 100 1500
5
10
15
20
25
30
0
20
40
60
80
100
120
Celerity (m/s)
Back Azimuth
Ele
vatio
n
-150 -100 -50 0 50 100 1500
5
10
15
20
25
30
200
220
240
260
280
300
320
340
360
380
Range (km)
Back Azimuth
Ele
vatio
n
-150 -100 -50 0 50 100 1500
5
10
15
20
25
30
0
50
100
150
200
250
300
350
400
450
500
Back Azimuth
Dat
e
I56USa Turning Point (km) from 5 degree elevation
-150 -100 -50 0 50 100 150
Oct02
Jan03
Apr03
Jul03
Oct03
Jan04
Apr04
Jul04
Oct04
Jan05
Apr05
Jul05
Oct05
Jan06
Apr06
Jul06
Oct06
Jan07
Apr07
0
20
40
60
80
100
120
Back Azimuth
Dat
e
I56US Turning Point (km) from 5 degree elevation
-150 -100 -50 0 50 100 150
Oct02
Jan03
Apr03
Jul03
Oct03
Jan04
Apr04
Jul04
Oct04
Jan05
Apr05
Jul05
Oct05
Jan06
Apr06
Jul06
Oct06
Jan07
Apr07
0
20
40
60
80
100
120
260 280 300 320 340 3600
20
40
60
80
100
120
-100 -50 0 50 1000
20
40
60
80
100
120
Sound Velocity (m/s) Wind Velocity (m/s)
Altit
ude
(km
)Zonal Meridional
Effective Sound Velocity (m/s)
Back Azimuth (Deg)
Alti
tude
(km
)
-150 -100 -50 0 50 100 1500
20
40
60
80
100
120
250
300
350
400
Jan03 Jul03 Jan04 Jul04 Jan05 Jul05 Jan06 Jul06 Jan07220
240
260
280
300
320
340
360
Date
Cel
erity
(m
/s)
I56US Eastward arrivals, 5 degree elevation
Jan03 Jul03 Jan04 Jul04 Jan05 Jul05 Jan06 Jul06 Jan07220
240
260
280
300
320
340
360
Date
Cel
erity
(m
/s)
I56US Southward arrivals, 5 degree elevation
Jan03 Jul03 Jan04 Jul04 Jan05 Jul05 Jan06 Jul06 Jan07220
240
260
280
300
320
340
360
Date
Cel
erity
(m
/s)
I56US Westward arrivals, 5 degree elevation
Jan03 Jul03 Jan04 Jul04 Jan05 Jul05 Jan06 Jul06 Jan07-5
-4
-3
-2
-1
0
1
2
3
4
5
Date
azde
verit
y (m
/s)
I56US Westward arrivals, 5 degree elevation
Azim
uth
Dev
iatio
n (d
egre
es)
Jan03 Jul03 Jan04 Jul04 Jan05 Jul05 Jan06 Jul06 Jan07-5
0
5
10
15
Date
azde
verit
y (m
/s)
I56US Southward arrivals, 5 degree elevation
Azim
uth
Dev
iatio
n (d
egre
es)
I55US Polar Latitude
Back Azimuth
Dat
e
I55USa Turning Point (km) from 5 degree elevation
-150 -100 -50 0 50 100 150
Oct02
Jan03
Apr03
Jul03
Oct03
Jan04
Apr04
Jul04
Oct04
Jan05
Apr05
Jul05
Oct05
Jan06
Apr06
Jul06
Oct06
Jan07
Apr07
0
20
40
60
80
100
120
200 250 300 3500
20
40
60
80
100
120
-50 0 500
20
40
60
80
100
120
Sound Velocity (m/s) Wind Velocity (m/s)
Altit
ude
(km
)Zonal
Meridional
Back Azimuth
Dat
e
I55US Turning Point (km) from 5 degree elevation
-150 -100 -50 0 50 100 150
Oct02
Jan03
Apr03
Jul03
Oct03
Jan04
Apr04
Jul04
Oct04
Jan05
Apr05
Jul05
Oct05
Jan06
Apr06
Jul06
Oct06
Jan07
Apr07
0
20
40
60
80
100
120
Jan03 Jul03 Jan04 Jul04 Jan05 Jul05 Jan06 Jul06 Jan07240
250
260
270
280
290
300
310
320
330
340
Date
Cel
erity
(m
/s)
I55US Southward arrivals, 5 degree elevation
Jan03 Jul03 Jan04 Jul04 Jan05 Jul05 Jan06 Jul06 Jan07240
250
260
270
280
290
300
310
320
330
340
Date
Cel
erity
(m
/s)
I55US Eastward arrivals, 5 degree elevation
Jan03 Jul03 Jan04 Jul04 Jan05 Jul05 Jan06 Jul06 Jan07220
240
260
280
300
320
340
Date
Cel
erity
(m
/s)
I55US Westward arrivals, 5 degree elevation
Jan03 Jul03 Jan04 Jul04 Jan05 Jul05 Jan06 Jul06 Jan07-5
0
5
10
15
Date
azde
verit
y (m
/s)
I55US Southward arrivals, 5 degree elevation
Azim
uth
Dev
iatio
n (d
egre
es)
Jan03 Jul03 Jan04 Jul04 Jan05 Jul05 Jan06 Jul06 Jan07-5
-4
-3
-2
-1
0
1
2
3
4
5
Date
azde
verit
y (m
/s)
I55US Westward arrivals, 5 degree elevation
Azim
uth
Dev
iatio
n (d
egre
es)
Conclusions• Over the past 5 years we have developed and compiled
reasonably good knowledge of the atmospheric state for infrasound propagation calculations.
• We have also developed and exercised robust procedures for calculating local infrasound propagation characteristics.
• Precomputed monthly average travel time tables and climatology are poor for operational infrasound source location calculations - performance of automated infrasound event association and source location algorithms will be greatly improved by the ability to continual update station travel time curves to properly account for the seasonal/daily/hourly changes of the atmospheric state
Challenges• Integration of propagation code/travel times
results into automated event association algorithms.
• Data volume and computational resource.• Validation, Validation, Validation