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Is a sum of random waves a good model of the
internal wave field?
or, an informal look at non-stationarity
Murray Levine
where
independent random variables
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u
time
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u-spectrum
frequency
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Interesting information in the
modulations?
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u-spectrum
frequency
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Random phase
u
time
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u
time
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High frequency Band
u-spectrum
time
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Random phase
u
time
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High frequency Band
u-spectrum
time
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So, look for the modulation of spectral bands
Are the modulations consistent with the random
wave model?
Use data from the Ocean Storms experiment Moored
Observations NE Pacific Ocean 47deg 25N, 139
deg 18W 1987-88
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10 month time series
Ocean Storms 194 m
u-spectrum
-2
Frequency, cph
0.1
1
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Spectrum as function of t, S(t)
Ocean Storms 194 m
u-spectrum
300
0
time, days
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Spectrum of S(t)
Ocean Storms 194 m
1/(300 days)
1/(10 days)
frequency
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Ocean Storms 2000 m
Spectrum as function of t, S(t)
u-spectrum
300
0
time, days
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Spectrum of S(t)
Ocean Storms 2000 m
u-spectrum
frequency
1/(300 days)
1/(10 days)
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Spectrum as function of t, S(t)
Random Model
u-spectrum
300
0
time, days
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Spectrum of S(t)
Random Model
1/(300 days)
1/(10 days)
frequency
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u-spectrum
frequency
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Another Random phase
u
time
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So, is the internal wave field look like this
random phase model? Ie is each freq band treated
this way Or is there information in the
modulations, ie the non-stationary part To
investigate this idea a bit further use data from
Ocean Storms experiment Open NE pacific,
1987-88, 47deg 25N 139 deg 18W
So, Look at time varying spectra and see if
random phase works. Ie, similar question can we
generate a realisitic iw field by random
phase? Or stated another way is there
information about the wave field in these
modulations Break up the spectrum into bins