Iterative surrogate cloud fields Victor Venema. Amplitude distribution Amplitude (LWP, LWC, )...
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Transcript of Iterative surrogate cloud fields Victor Venema. Amplitude distribution Amplitude (LWP, LWC, )...
Iterative Iterative surrogate cloud fieldssurrogate cloud fields
Victor VenemaVictor Venema
Amplitude distributionAmplitude distribution Amplitude (LWP, LWC, Amplitude (LWP, LWC, ) alone is ) alone is
already good: See Independent Pixel already good: See Independent Pixel Approximation (IPA)Approximation (IPA)
Especially very important are the cloud Especially very important are the cloud free portionsfree portions
Together with power spectrum it also Together with power spectrum it also ‘defines’ the structure‘defines’ the structure
Measured power spectrumMeasured power spectrum Fractal power spectrum?Fractal power spectrum? Measured power spectrumMeasured power spectrum
– Scale breaksScale breaks– WavesWaves– ……
Satellite pictures: Eumetsat
Iterative algorithmIterative algorithm
Add an dimensionAdd an dimension Assume isotropyAssume isotropy Rotate and scale power spectrumRotate and scale power spectrum
1000 2000 3000 4000 5000 6000 7000 80000
100
200
300
400
500
Time (s)
LWP
(gr
/m2 )
Time (s)
Tim
e (s
)
2000 4000 6000 8000
1000
2000
3000
4000
5000
6000
7000
8000 0
100
200
300
400
500
3D surrogate clouds3D surrogate clouds
Time [hr] UT
Hei
ght
[km
] LWC template [kg/m3]
10.5 11
1.4
1.6
1.8
2
2.2
0
0.1
0.2
0.3
0.4
0.5
LWC Surrogate
0 2 4 60
2
4
6
0
2
4
6
0 2 4 61.5
2
Reff
Surrogate
0 2 4 60
2
4
6
0
2
4
6
0 2 4 61.5
2
Time [hr] UT
Hei
ght
[km
]
LWC template [kg/m3]
13.2 13.41
1.5
2
0
0.5
1
1.5
LWC Surrogate
0 2 4 6 80
2
4
6
8
0
2
4
6
8
0 2 4 6 81
1.52
Reff
Surrogate
0 2 4 6 80
2
4
6
8
0
2
4
6
8
0 2 4 6 81
1.52
Time [hr] UT
Hei
ght
[km
]
LWC template [kg/m3]
7 7.5
0.5
0.6
0.7
0.8
0.9
0
0.5
1
1.5
LWC Surrogate
0 5 100
5
10
0
5
10
0 5 10
Reff
Surrogate
0 5 100
5
10
0
5
10
0 5 10
Time [hr] UT
Hei
ght
[km
]
LWC template [kg/m3]
9 9.5
0.4
0.6
0.8
0
0.2
0.4
0.6
LWC Surrogate
0 5 100
5
10
0
5
10
0 5 100.40.60.8
Reff
Surrogate
0 5 100
5
10
0
5
10
0 5 100.40.60.8
Validation surrogate cloudsValidation surrogate clouds 3D LWC fields from LES modelling3D LWC fields from LES modelling Make surrogates from their statisticsMake surrogates from their statistics Calculate radiative propertiesCalculate radiative properties
– RadiancesRadiances– IrradiancesIrradiances– Actinic fluxesActinic fluxes
Compare themCompare them
Surrogate stratocumulusSurrogate stratocumulusTemplatesTemplates SurrogatesSurrogates
Reflectance template and Reflectance template and surrogate stratocumulussurrogate stratocumulus
0.3 0.4 0.5 0.6 0.7
0.3
0.4
0.5
0.6
0.7re
flect
ance
sur
roga
te
reflectance template
(a)
Surrogate cumulus - oldSurrogate cumulus - oldTemplatesTemplates SurrogatesSurrogates
Surrogate cumulus – radianceSurrogate cumulus – radiance
0.005 0.01 0.015 0.02
0.005
0.01
0.015
0.02
radiance template cumulus [W m-2 sr-1]
radi
ance
sur
roga
te [W
m-2
sr-1
]
Validation cumulus - newValidation cumulus - new Developed a more Developed a more
accurate Stochastic accurate Stochastic IAAFT algorithmIAAFT algorithm
Surrogates are Surrogates are copies of templatescopies of templates
In practise the bias In practise the bias is likely still there as is likely still there as you cannot measure you cannot measure the power spectrum the power spectrum that accuratelythat accurately
Validation broken cloudsValidation broken clouds
Scanning measurementsScanning measurements Structure maintaining interpolationStructure maintaining interpolation Anisotropic power spectrumAnisotropic power spectrum More samplesMore samples Better Better
decorrelationdecorrelation
Scanning measurementsScanning measurements Scanning Scanning
measurementmeasurement– Amplitude distribution Amplitude distribution – 2D power spectrum2D power spectrum
Force the measured Force the measured values on the spiralvalues on the spiral
Measured: Measured: 16.5 %16.5 %
Scanning measurementsScanning measurements
Surrogate with cloud mask
ConclusionsConclusions IAAFT algorithmIAAFT algorithm
– Full 3D structureFull 3D structure– LWC height profileLWC height profile– Local forcing of measurementsLocal forcing of measurements– FlexibleFlexible
DimensionsDimensions MeasurementsMeasurements Vary the statistics independentlyVary the statistics independently
Validated for Sc and sparse CuValidated for Sc and sparse Cu– Cloud cover > 80%, <20%Cloud cover > 80%, <20%
3D Cloud fields based on the BBC and 3D Cloud fields based on the BBC and BBC2 campaign on the BBC-serverBBC2 campaign on the BBC-server
OutlookOutlook Improve convergence for broken cloudsImprove convergence for broken clouds Validate for broken cloudsValidate for broken clouds Iterative wavelet surrogatesIterative wavelet surrogates Constrained surrogatesConstrained surrogates Sebastián Gimeno García: 2D and 3D Sebastián Gimeno García: 2D and 3D
radiative transferradiative transfer Sebastian Schmidt: 3D surrogates from Sebastian Schmidt: 3D surrogates from
in situ measurementsin situ measurements 3D Surrogates from scanning 3D Surrogates from scanning
measurementmeasurement
Comparison cloud generatorsComparison cloud generators Reviewer: “It is not clear why this technique is an
improvement over simpler approaches.”
IAAFT methodIAAFT method Cumulus fields (Evans; structure of a binary mask)Cumulus fields (Evans; structure of a binary mask)
CALBAUTAIR (Schreirer and Schmidt)CALBAUTAIR (Schreirer and Schmidt) Shift cloud (Schmidt; Los and Duynkerke)Shift cloud (Schmidt; Los and Duynkerke) 2D-2D Ice cloud (Liou et al.)2D-2D Ice cloud (Liou et al.)
tdMAP (tdMAP (A. Benassi, F. Szczap, et al.)A. Benassi, F. Szczap, et al.) Multi-fractal cloudsMulti-fractal clouds Bounded Cascade and other fractal cloudsBounded Cascade and other fractal clouds Fourier methodFourier method
– SITCOM (F. di Giuseppe; 2D structure)SITCOM (F. di Giuseppe; 2D structure)– Ice clouds (R. Hogan, S. Kew; 2.5D structure)Ice clouds (R. Hogan, S. Kew; 2.5D structure)
3SPL3SPL3SP3SP
3_PL3_PL2__L2__L2__L2__L
2SP_2SP_2SP_2SP_2S__2S__2S__2S__
Bounded CascadeBounded Cascade It is a power spectral method just as It is a power spectral method just as
the Fourier methodthe Fourier method The amplitude distribution is fixed, The amplitude distribution is fixed,
‘Log-normal like’‘Log-normal like’ Why take block functions?Why take block functions? At least for the Fourier method there is At least for the Fourier method there is
a large amount of literaturea large amount of literature But Bounded Cascade clouds are But Bounded Cascade clouds are
fractals!!fractals!!
1D Iterative LWP surrogates1D Iterative LWP surrogates
1000 2000 3000 4000 5000 6000 7000 80000
100
200
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400
500
Time (s)
LWP
(gr
/m2 )
1000 2000 3000 4000 5000 6000 7000 80000
100
200
300
400
500
Time or space
LWP
or
LWC
1D Iterative LWP surrogates1D Iterative LWP surrogates
1000 2000 3000 4000 5000 6000 7000 80000
100
200
300
400
500
Time (s)
LWP
(gr
/m2 )
1000 2000 3000 4000 5000 6000 7000 80000
100
200
300
400
500
Time or space
LWP
or
LWC
0 500 1000 1500 2000 2500 3000 35000
100
200
300
400
500
600
Number
LWP
(gr
/m2 )
MeasuredSurrogate
10-3
10-2
10-1
10-5
100
105
k (Hz)
Pow
er
MeasuredSurrogate
2D Iterative LWP surrogates2D Iterative LWP surrogates
1000 2000 3000 4000 5000 6000 7000 80000
100
200
300
400
500
Time (s)
LWP
(gr
/m2 )
Time (s)
Tim
e (s
)
2000 4000 6000 8000
1000
2000
3000
4000
5000
6000
7000
8000 0
100
200
300
400
500
Conclusions and outlookConclusions and outlook Improve convergenceImprove convergence Cumulus fields are very intermittantCumulus fields are very intermittant
– Smooth clear sky partSmooth clear sky part– Structured cloudy partStructured cloudy part
Maybe iterative wavelet surrogates Maybe iterative wavelet surrogates would converge bettterwould converge bettter
Evolutionary search algorithm doesn‘t Evolutionary search algorithm doesn‘t get easily stuck in local minimaget easily stuck in local minima