1

NVBM Symposium – 6 November 2009

O.K. Hartogensis

Ontwikkelingen in de Scintillometrie

2

Enige Conclusies ter Introductie

• Scintillometers meten de verticale voelbare en latente warmtestroomover “grote” gebieden (schaal: 0.1 - 10km)

• Er zijn verschillende scintillometers voor diverse toepassingen (b.v.. lang vs kort pad en soort fluxen)

• Scintillometer methode is heel eenvoudig:Methode kan worden toegepast door non-experts in micro-meteoInstrumenten zijn makkelijk in onderhoudData processing is “eenvoudig”

• Scintillometer method is ook zeer complex:Wave propagation theory in turbulent mediumMicro-meteorologie: Turbulentie in de oppervlaktelaag

3

What are Scintillations?

Scintillometry

4

• Scintillometer length scales: L (path length), λ (wavelength), F (Fresnel length) = (λL)1/2, D(aperture), z (height)• Turbulence length scales: l0 (inner length scale), L0 (outer length scale)

Scintillometer schematic + Length Scales

Scintillometry

5

Scintillometry in a nutshell

Scintillometry

I

II

III

Intensity fluctuationsexpressed as σln(I)

CT2 or Cq2

H and LvE (and u*)

Transmitter

Receiver

λ MOST

Cn2

Turbulence +Wave Prop. Theory

(and l0)

(and ε)

( ) ( )32

12

2212 ][

rrnrnCn

−=

(and τ)

D +

6

I Wave Propagation Theory + Turbulence – Many eddies

Scintillometer Equation: ( ) ( )( )∫ ∫

∞

−=L

I dkdxLkDx

LkDxJKL

xLxkkK0 0

2

21

2222

)ln( 2/2/4

2sin16πσ φn

n-spectrum

• Scintillometer sensitive to one eddy scale: largest of D or F= (λL)1/2

• If in Inertial range →

• If in Dissipation range →

3/112033.0 −= kCnnφ( )03/112033.0 klfkC Ann

−=φ

Scintillometry

Inertial Range – KolmogorovDissipation Range - Hill

Production DissipationInertial Range

φ n

kL0 l0

3/112033.0 −kCn

7

Scintillometer Types

Optical Scintillometers:Temperature fluctuations → H (and u*)

RadioWave Scintillometers:Humidity fluctuations → LvE

LAS – Large Aperture ScintillometerXLAS – Extra large Aperture ScintillometerDBLS – Displaced Beam Laser Scintillometer

MWS – Micro-Wave Scintillometer

Type D λ L

LAS 15 cm ≈1µm 1- 5 km

XLAS 30 cm ≈1µm 5 – 10 km

MWS 15 cm ≈1 cm 1 -10 km

DBLS 2.5 mm 0.7 µm 100 m

Research

Scintillometer types defined by: D and λ

8

• People• Current Research

Scintillometer work by MAQ

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People – “the Godfathers” (now pensionados)

Wim Kohsiek – KNMI/MAQ Henk de Bruin – MAQ

10

People – the Builders

Bert Heusinkveld

Willy Hillen

Frits Antonysen

Kees van den Dries

11

People – the PhD’s + PostDocs

Oscar Hartogensis

Wouter Meijninger

Joost Nieveen

Arnold Moene

Arjan van Dijk Bram van Kesteren

12

STW-Project – Innovations in Scintillometry (2008-2012)

Measure H + LvE + u* at field scale:Short Path Scintillometer (SPS)

combination of number of beams and or receivers

additional measurements forevapotranspiration

Measure H + LvE directly at km-scale: Optical-Millimetre wave System (OMS):

Refractive index in millimeter-wave range dependent on water vapour andtemperature

Research

13

MWS & LAS Transmitter

MWS & LAS Receiver

λ2 = 930 nm

λ2 = 11 mm

Intensity fluctuations

var [ln(I1)] var [ln(I2)] cov [ln(I1, I2)]

Cn12 Cn22 Cn1,n2

Turbulence + Wave Prop. Theory

CT2 Cq2 CTq

U, roughness parameters + MOST

H LvE

Scintillometry

OMS system – Third Equation – Full OMS method

“Full” OMS methodLudi et al (2005) BLM117

14

Chilbolton Experiment – field site Rutherford Appleton Laboratory (RAL)

Experiment

15

Chilbolton Experiment – field site Rutherford Appleton Laboratory (RAL)

Experiment

16

Open door laboratory

Test range of 500m long

2 opposite cabins at 4m height

Chilbolton Experiment – the Site

Experiment

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Chilbolton Experiment – Scintillometers

• CEH-RAL94 MWS – 94Ghz – GPS pulse to lock transmitter and receiver frequency

• Kipp&Zn LAS – 880nm - Fresnel lens to focus beam onto detector

• Wageningen LAS – 940nm – Concave mirror to focus beam onto detector

• datalog units in both cabins – 500Hz – GPS pulse to synchronize the signals

Experiment

18

Chilbolton Experiment – local turbulence measurements

• CSAT3 sonic + LiCor 7500

• 3 fine wire thermocouples

• datalog unit – 20Hz

Reference for Fluxes and Structure parameters

Experiment

19

• Evidence of Absorption

•“simple filter”: 10s moving average

10-4

10-2

100

102

0

20

40

60

80

100

120

f - natural frequency [Hz]

f*S

(f) -

spec

tral d

ensi

ty [v

aria

nce]

Non-FilteredFiltered

10-4

10-2

100

102

10-4

10-2

100

102

104

f - natural frequency [Hz]

S(f)

- sp

ectra

l den

sity

[var

ianc

e/H

z]

-8/3Non-FilteredFiltered

10-4

10-2

100

102

10-4

10-2

100

102

104

f - natural frequency [Hz]S

(f) -

spec

tral d

ensi

ty [v

aria

nce/

Hz]

-8/3Non-FilteredFiltered

Chilbolton Results – CEH-RAL94 Spectra

10-4

10-2

100

102

0

5

10

15

f - natural frequency [Hz]

f*S

(f) -

spec

tral d

ensi

ty [v

aria

nce]

Non-FilteredFiltered

Results

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Chilbolton – OMS Evaporation

No Absorption Filter

• OMS system: CEH-RAL94 MWS and Wag LAS• 10s moving average filter for RAL94• No Cn1n2 used; RTq from EC system

With Absorption Filter

0 100 200 3000

50

100

150

200

250

300

350

y = 0.79x + 49R2 = 0.35

(a)

LvEEC (W/m2)

LvE

OM

S (W/m

2 )

0 100 200 3000

50

100

150

200

250

300

350

y = 0.68x + 23R2 = 0.59

(b)

LvEEC (W/m2)

LvE

OM

S (W/m

2 )

Results

21

Final Remarks

• First results of evaporation by the OMS system look “promising”. • Further refinements we work on:

– Compare results with local turbulence measurements at structure parameter level.

– “Full” OMS method with Cn1,n2

– Filtering LAS and MWS by routinely fitting theoretical to measured spectrum:

10-2

100

102

10-4

10-2

100

102

104

f - natural frequency [Hz]

S(f)

- sp

ectra

l den

sity

[var

ianc

e/H

z]

Spectrum optical scintillometer on day of year 245 from 1010 to 1020 UTC

MWSLASModel

10-2

100

102

10-5

10-4

10-3

10-2

10-1

100

101

102

103

f - natural frequency [Hz]

S(f)

- sp

ectra

l den

sity

[var

ianc

e/H

z]

Spectrum optical scintillometer on day of year 245 from 720 to 730 UTC

MWSLASModel

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DBLS Transmitters

DBLS Receivers

λ= = 670 nm

λ || = 670 nm

Intensity fluctuationsvar [ln(I||)] var [ln(I=)] cov [ln(I||, I=)]

l0Cn2

Turbulence + Wave Prop. Theory

CT2

H

ε

MOST

u*

Double Beam Laser Scintillometer (DBLS)

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Combination Methods: Scinti–Variance + Scinti–Structure-Parameter

xx quF **ρ=MOST framework:

Variance: ( )211 )()( rxrxx −=σ ( )Lzfq xx

x

x /*

=σ

Structure parameters:( )

3/212

2212 )()(

rrxrxCx

−= ( )Lzf

qzC

xx

x /2*

3/22

=

Scalar turbulence measurements:

Scintillometer: u* + L

σT + σq + σqCO2

Hu

gTcL p

3*

κρ−=with

CT2 + Cq

2 + CqCO22

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Merken Set-up

Scintillometry

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Combination-Methods – Long Interval (30min)

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Combi-Methods – Long Interval (30min)

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Space AND time averaging of turbulence

Non-Stationary Turbulence

-80

-60

-40

-20

0

20

18 21 0 3 6 9Local Time (CDS)

Hsc

intil

lom

eter

[W m

-2]

-160

-120

-80

-40

0

18 21 0 3 6 9Local Time (CDS)

Hed

dy_c

ovar

ianc

e [W

m-2

]

-80

-60

-40

-20

0

20

18 21 0 3 6 9Local Time (CDS)

Hsc

intil

lom

eter

[W m

-2]

-80

-60

-40

-20

0

20

18 21 0 3 6 9Local Time (CDS)

Hed

dy_c

ovar

ianc

e [W

m-2

]

-80

-60

-40

-20

0

20

18 21 0 3 6 9Local Time (CDS)

Hsc

intil

lom

eter

[W m

-2]

-80

-60

-40

-20

0

20

18 21 0 3 6 9Local Time (CDS)

Hed

dy_c

ovar

ianc

e [W

m-2

]

Scintillometer Eddy-Covariance

6 sec

1 min

30 min

-80

-60

-40

-20

0

20

18 21 0 3 6 9Local Time (CDS)

Hsc

intil

lom

eter

[W m

-2]

-160

-120

-80

-40

0

18 21 0 3 6 9Local Time (CDS)

Hed

dy_c

ovar

ianc

e [W

m-2

]

-80

-60

-40

-20

0

20

18 21 0 3 6 9Local Time (CDS)

Hsc

intil

lom

eter

[W m

-2]

-80

-60

-40

-20

0

20

18 21 0 3 6 9Local Time (CDS)

Hed

dy_c

ovar

ianc

e [W

m-2

]

-80

-60

-40

-20

0

20

18 21 0 3 6 9Local Time (CDS)

Hsc

intil

lom

eter

[W m

-2]

-80

-60

-40

-20

0

20

18 21 0 3 6 9Local Time (CDS)

Hed

dy_c

ovar

ianc

e [W

m-2

]

Scintillometer Eddy-Covariance

6 sec

1 min

30 min

28

Objective

Test alternative methods to determine turbulent H2O and CO2 fluxes, which have a faster statistical convergence than the classical eddy-covariance method.

29

Combi-Methods – Short Intervals (1 min) – Temporal Variation

0

250

500

750

L vE +

Qne

t(W m

-2)

0

250

500

750

L vE +

Qne

t(W m

-2)

0

250

500

750

L vE +

Qne

t(W m

-2)

0

250

500

750

L vE +

Qne

t(W m

-2)

0

250

500

750

2271030

2271100

2271130

2271200

2271230

2271300

2271330

DOY - Time (UTC)

L vE +

Qne

t(W m

-2)

LvEEC

LvEVarBow en

LvEVarianceLvEStrucPar

LvEBudget

Qnet

EC

Bowen

σx

Cx2

Energy balance

LvE

30

Combi-Methods – Short Intervals (1 min) – Temporal Variation

0

0.5

1

1.5

2

-FCO

2 (mg

m-2

s-1

)

0

200

400

600

800

Q ne

t (W m

-2)

0

0.5

1

1.5

2

-FCO

2 (mg

m-2

s-1

)

0

200

400

600

800

Q ne

t (W m

-2)

0

0.5

1

1.5

2

-FCO

2 (mg

m-2

s-1

)

0

200

400

600

800

Q ne

t (W m

-2)

0

0.5

1

1.5

2

-FCO

2 (mg

m-2

s-1

)

0

200

400

600

800

2271030

2271100

2271130

2271200

2271230

2271300

2271330

DOY - Time (UTC)

Q ne

t (W m

-2)

FCO2EC

FCO2VarBow en

FCO2Variance

FCO2StrucPar

Qnet

EC

Bowen

σx

Cx2

-FCO2

31

Conclusions

• Combined Methods work!

• Combined Method indeed gives much more reliable

minute interval mass fluxes than EC

• Mr wrk ndd

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KvK - WindVisions (2010-2014)

Wind and Visibility monitoring system at Schiphol Airport

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End