Study of atmospheric
phenomena and structure
using the USArray
Transportable Array
Michael A.H. Hedlin &
Catherine D. de Groot-Hedlin
Laboratory for Atmospheric Acoustics
Inst. of Geophysics and Planetary Physics
University of California, San Diego
Content
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•
•
•
Infrasound
The seismo-acoustic TA and AELUMA
Finding acoustic sources over the US
Study of atmospheric gravity waves
The Acoustic Spectrum
Very
deep
rumble
is here
Some Infrasound Sources
Air temperature
100
km
Altitude
50 km --0 km -
Cool
Thermosphere
Mesosphere
Stratosphere
Troposphere
Warm
The speed of sound
100
km
Altitude
50 km --0 km -
Thermosphere
Mesosphere
Stratosphere
-
Troposphere
260 m/s
380 m/s
Sound speed depends
on direction it travels
Wind
Source
The Global Seismographic Network
IMS Infrasound Network
Infrasound Network
TA sites with atmospheric sensors
TA sites with atmospheric sensors
IMS infrasound arrays
Addition of atmospheric sensors
Setra Barometer
EP - LDO, EP - BDO
NCPA Infrasound Microphone
EP - LDF, EP - BDF
MEMS Barometer
EP - LDM
13
13
From Bob Busby
Overlapping pass-bands provides continuous coverage from DC to 20 Hz
Detecting/locating infrasonic events
TA sites in 2013
> 500 sites
Triads available in 2013
> 1,000 triads
shown here
Triads available in 2013
> 1,000 triads
shown here
Example event: a bolide
JD 271, 2013
de Groot-Hedlin and Hedlin, GJI (2015)
Example event: a bolide
de Groot-Hedlin and Hedlin, GJI (2015)
2-8 Hz acoustic catalog
2,220 events in 2013
de Groot-Hedlin and Hedlin,
GJI (2015)
90° W
70° W
2-8 Hz acoustic catalog
Jan 1
Dec 31
2,220 events in 2013
de Groot-Hedlin and Hedlin,
GJI (2015)
Some of these events are huge
20:56 UT
JD 302, 2013
Some of these events are huge
2,000 km
20:56 UT
JD 302, 2013
1,000 km
de GrootHedlin and
Hedlin, GJI
(2015)
Some of these events are huge
2,000 km
20:56 UT
JD 302, 2013
1,000 km
Wind
Wind
Histogram of acoustic activity
2012-2014
Study of atmospheric gravity waves
Background: Liu et al. (2014), Gravity waves simulated by highresolution Whole Atmosphere Community Climate Model,
Geophysical Research Letters
Atmospheric gravity waves
2-4 hour
Atmospheric gravity waves
2-4 hour
Atmospheric gravity waves
2-4 hour
Atmospheric gravity waves
2-4 hour
Atmospheric gravity waves
2-4 hour
Atmospheric gravity waves
2-4 hour
Atmospheric gravity waves
Delauney
triangulation
defines 580 threeelement arrays
de Groot-Hedlin et
al., EPSL, 2013
de Groot-Hedlin et
al., EPSL, 2013
de Groot-Hedlin et
al., EPSL, 2013
de Groot-Hedlin et
al., EPSL, 2013
de Groot-Hedlin et
al., EPSL, 2013
de Groot-Hedlin et
al., EPSL, 2013
de Groot-Hedlin et
al., EPSL, 2013
de Groot-Hedlin et
al., EPSL, 2013
de Groot-Hedlin et
al., EPSL, 2013
de Groot-Hedlin et
al., EPSL, 2013
Case studies: Comparison with satellite observations
Gravity waves observed at ground
level using the TA
Gravity waves observed in the
stratosphere from space
From Lars Hoffmann
Case studies: Comparison with satellite observations
Gravity waves observed at ground
level using the TA
Gravity waves observed in the
stratosphere from space
From Lars Hoffmann
Long-term occurrence of gravity waves
2010-2014 TA – over 3,000 triads
Gravity wave occurrence
Observed on ground by TA 2010-2014
Gravity wave occurrence
Observed on ground by TA 2010-2014
Observed in stratosphere in summer months/nighttime
by AIRS sensor 2003-2011
From Lars Hoffmann
Summary
• The dense seismo-acoustic TA permits new lines
of research
• The triad method can be adapted to a range of
pressure/acoustic/seismic networks
• The extended triad method (AELUMA) reveals
several “acoustogenic” regions in the eastern
US
– Some particularly large events
– Some repeating source regions
• Preliminary study of gravity waves in the
eastern US shows general agreement with
satellite data
Project is supported by NSF contract EAR-1358520