Problems in Atmospheric Sciences:

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Problems in Atmospheric Sciences Potential
Utility of Infrasound Data

• Midlatitude Cyclones
• Tropical Cyclones
• WW3 Microbaroms

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Forecast Errors over Pacific
West Coast Forecast Bust a Costly Embarrassment
in Eugene, Ore.
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Forecast Errors over Pacific
L
976
NCEP Eta model 24-hr (solid) and 48-hr (dashed)
SLP forecast (mb) for 00 UTC on 3 March 1999 and
GOES infrared satellite image.
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Forecast Errors over Pacific
24-hr (top) and 48-hr (bottom) SLP forecast
errors (mb) for period 11/01-04/02.
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Forecast Busts
Model 48-hr forecast (solid) and analysis
(dashed) of Sea Level Pressure (every 2 mb) for
14 December 2001
Eta
AVN
NOGAPS
UKMO
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Forecast Errors over Pacific
Model storm forecast central SLP errors (mb) and
storm position errors for period 00 UTC 14 Dec
2001.
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Lightning Detection
This noise can be detected by a network of
special receivers located on remote Pacific
islands.
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Lightning Detection Project (ONR)
Noise from lightning measured by PACNET can be
used to estimate the rainfall rate.
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Sea-level Pressure Map at 18 UTC (left panel) and
Long Range Cloud-to-ground Lightning Detected
between 1453 and 1753 UTC (right panel) 18
December 2002.
Pacific Extratropical Cyclone
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Sea-level Pressure Map at 3 UTC (left panel) and
Long Range Cloud-to-ground Lightning Detected
between 2353 and 0253 UTC (right panel) 18-19
December 2002.
Pacific Extratropical Cyclone
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Sea-level Pressure Map at 6 UTC (left panel) and
Long Range Cloud-to-ground Lightning Detected
between 0253 and 0553 UTC (right panel) 19
December 2002.
Pacific Extratropical Cyclone
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Sea-level Pressure Map at 9 UTC (left panel) and
Long Range Cloud-to-ground Lightning Detected
between 0553 and 0853 UTC (right panel) 19
December 2002.
Pacific Extratropical Cyclone
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Sea-level Pressure Map at 12 UTC (left panel) and
Long Range Cloud-to-ground Lightning Detected
between 0853 and 1153 UTC (right panel) 19
December 2002.
Pacific Extratropical Cyclone
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Sea-level Pressure (SLP) Map at 12 UTC (left
panel) and Eta SLP Forecasts valid at 12 UTC (24
and 12 hr forecasts shown in middle and far right
panels, respectively) 19 December 2002.
Pacific Extratropical Cyclone
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Forecasting a Kona low
AVN Forecast Pressure Traces
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Winter Storm Summary

• Large short-term (0-48 hr) forecast errors (gt10
  mb) occur 10-15 times each winter over the
  northeast Pacific in the Eta model.
• Large initialization errors over the Pacific
  still occur in all operational forecast systems
  and are major contributors to short-term forecast
  failures.
• Occasionally small initial errors grow into large
  forecast errors.
• Large position errors of surface low centers
  contribute to large forecast errors of SLP at
  coastal locations.
• Forecast failures over the eastern Pacific Ocean
  propagate downstream and can contribute to large
  forecast errors over the eastern half of the U.S.
• Is there a role for infrasound in toward solving
  this problem?

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The Hurricane Problem
What do we know about hurricanes?
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Hurricane Track Forecasting
Track forecasts from numerical and statistical
models are compared to come up with the best
forecast track.
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Hurricane Track Forecasting
Hurricanes track forecasting has made significant
gains in the past 30 years due to faster
computers and better observations of storm
steering currents by aircraft and satellite
instruments.
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Hurricane Intensity Forecasting
Hurricanes intensity forecasting has made almost
no gains in the past 30 years despite faster
computers and better observations of storm
environment by aircraft and satellite
instruments. Part of problem is a lack of
understanding of energy transfer from ocean to
atmosphere, which in turn depends on the
particulars of the boundary layer structure and
circulation.
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Radar Analysis
Doppler Velocity
A residual velocity for each elevation is
obtained by subtracting the 0th order
(sinusoidal) component of the velocity field as
observed by the radar along a conical scan of set
elevations.
Residual Velocity
VAD Velocity
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Animation of Velocity Residuals in Hurricane
Bonnie
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Boundary Layer Rolls Characteristics
Schematic depicting hurricane boundary layer
rolls, showing the mean values for 142 BL rolls
observed during four hurricane landfalls (142
cases).
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Developing a Hurricane Balloon to study
Lagrangian enegetics of airflow
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Developing a Hurricane Balloon

• GPS position
• Satellite cellular telephone for communication
• Lift control
• Lots of sensors
• Microphone?

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Developing a Hurricane Balloon
Release in Hawaii
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What are microbaroms?

• Microbaroms signals, like microseisms, are
  believed to be created by the nonlinear
  interaction of ocean surface waves
• The microbarom peak near 0.2 Hz is right on the
  detection frequency band for 1 kt explosions
• IMS arrays with large apertures (gt 1 km) were
  supposed to render microbaroms incoherent, but
  distinct coherent bursts may still be detected
• Microbaroms may be generated in open ocean or by
  reflections with coastline and islands, and are
  prominent on island stations
• Theoretical energy peak of microbarom radiation
  is near vertical, but this energy is lost
• Sufficient energy is radiated near the
  horizontal, where most microbarom arrivals are
  detected
• Study microbarom statistics at I59US and global
  distribution of microbarom signal levels

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Microbaroms 2002
N Swells, Aleutians
Trade and S Swells
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Theory Arendt and Fritz, 2000

• Assumptions
• Wave height small relative to wavelength of ocean
  wave
• Distance greater than acoustic wavelength

• Solution
• For a prescribed surface wave displacement g(x,t)
  and vertical velocity uz(x,t), the acoustic
  pressure is

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Theory

• Consider a ocean surface wave displacement
  spectrum A,

The radiated acoustic spectrum would be
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Wave Watch 3 (WW3)

• WAVEWATCH III (Tolman 1997, 1999a) is a third
  generation wave model developed at NOAA/NCEP.
• WAVEWATCH III solves the spectral action density
  balance equation for wavenumber-direction
  spectra. The implicit assumption of these
  equations is that the medium (depth and current)
  as well as the wave field vary on time and space
  scales that are much larger than the
  corresponding scales of a single wave.
  Furthermore, the physics included in the model do
  not cover conditions where the waves are severely
  depth-limited. This implies that the model can
  generally by applied on spatial scales (grid
  increments) larger than 1 to 10 km, and outside
  the surf zone.

http//polar.ncep.noaa.gov/waves/wavewatch/
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Young Swell case (0-4 days old)
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Middle Age Swell case (4-6 days old) All with
identical forcing
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Old Swell case (6-10 days old) All with identical
forcing
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Atmospheric Forcing
Surface winds associated with January 2003 Case
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Wave Watch 3 (WW3)
Wave height and dominant period
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January 2003 Case
Wave Spectra
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January 2003 Case
Microbarom arrivals
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Fig. 2 Observed infrasonic arrival azimuth for
microbarom signals (0.1-0.5Hz) in comparison with
azimuth from Hawaii to Hurricane Daniels core
(Red Line).
Fig. 1 Hurricane Daniel as seen by GOES 10 on
July 26, 2000. ISLA will attempt to accurately
depict the wind/wave field produced by Hurricane
Daniel in order to model microbaroms produced by
the nonlinear interaction of Daniels ocean
surface waves.
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Evaluating the Theoretical Model
The Wave Watch 3 model outputs the variance
density , F, of the surface wave field as a
function of frequency, f, and propagation
direction,q. The variance density can be
integrated over angle and frequency to provide
the total wave energy E,
The peak source pressure occurs when k -k, w
w
For preliminary amplitude estimates, we use
Whitakers relationship
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Global Pressure Field Frequency steps of 0.01 Hz
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Predicted vs Observed
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Microbarom Conclusions and future work

• All IMS infrasound arrays, and particularly those
  close to the ocean, are susceptible to
  microbaroms
• Surface wave spectrum from Wave Watch 3 global
  model
• Algorithm to evaluate a theoretical source
  pressure field induced by the open ocean surface
  wave field
• Used simple relationship to estimate global
  infrasonic field
• Need to add atmospheric specifications,
  attenuation losses, and direction of arrival
  information
• Need to incorporate better propagation algorithms
  to provide time dependent and frequency dependent
  estimates of the propagating infrasonic field
• Need to add reflections with coastline and
  islands mesoscale problem, site dependent and
  not trivial
• Approach can be adapted to microseisms

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Time for Barnstorming?