quality controlled data base of the cops surface energy balance network

Thomas [email protected]

University of Bayreuth – Department of Micrometeorology www.bayceer.uni-bayreuth.de/mm

Bayreuth Center of Ecology and Environmental Research

Quality controlled data base of the COPS surface energy balance network

Thomas Foken, Rafael Eigenmann Dept. Micrometeorology, University of Bayreuth

www.bayceer.uni-bayreuth.de/mm

7th COPS Workshop 27th-29th October 2008, Strasbourg




Content

• Energy balance group: an overview• Turbulence data processing• Turbulence quality control:

– Part 1: Turbulence flux calculation– Part 2: Footprint analysis– Part 3: Internal boundary layer evaluation

• WDCC data base • Conclusion




Energy balance network

• Organisation: http://www.bayceer.uni-bayreuth.de/COPS/




Energy balance network - WEB




Turbulence data processing with TK2

Processing steps and applied flux corrections:– Calculation of averages, variances and covariances for

30 min averaging intervals– Correction of a time delay between different sensors

by cross correlation– Spike test– Cross-wind correction– Planar fit coordinate rotation– Correction of spectral loss– Conversion of buoyancy into sensible heat flux– WPL correction

(Vickers and Mahrt, 1997)

(Wilczak et al., 2001)

(Moore, 1986)

(Schotanus et al., 1983; Liu et al., 2001)

(Webb et al., 1980; Fuehrer and Friehe, 2002; Liebethal and Foken, 2003, 2004)




EC-data quality checkTest on steady state conditions

iiM

j jj

jjNjjNi

yxyx

yxyxyx

''''

''

1

11

1

i ijj

jjNM

ii jjjNM

yxyxyx 11

1''

(Foken and Wichura, 1996, Foken et al. 2004)




EC-data quality check Test on developed turbulence


21

*

,, cwvuLzcu

21

*

cT

LzcT

parameter z/L c1 c2

σW/u* 0 > z/L > -0,032-0,032 > z/L

1,32,0

01/8

σu/u* 0 > z/L > -0,032-0,032 > z/L

2,74,15

01/8

σT/T* 0,02 < z/L < 10,02 > z/L > -0,062-0,062 > z/L > -1

-1 > z/L

1,40,51,01,0

-1/4-1/2-1/4-1/3




quality class steady state integral turbulence charactersitics

1 1 1–2 2 2 1–2 3 1–2 3–4 4 3–4 1–2 5 1–4 3–5 6 5 ≤ 5 7 ≤ 6 ≤ 6 8 ≤ 8 ≤ 8 9 one parameter 9 9

EC-data quality check Overall flagging of data





quality class steady state integral turbulence charactersitics

1 1 1–2 2 2 1–2 3 1–2 3–4 4 3–4 1–2 5 1–4 3–5 6 5 ≤ 5 7 ≤ 6 ≤ 6 8 ≤ 8 ≤ 8 9 one parameter 9 9

EC-data quality check Overall flagging of data

good

moderate

bad

do not use





Turbulence data quality (I)

• Post-field quality control

– Steady state test– Test for integral turbulence

characteristics

combined flag (1 to 9)

will be uploaded to the WDCC

data base within a flux NetCDF-file

Classes 1-3: suitable for fundamental researchClasses 4-6: only for monthly or annual sumsClasses 7-8: rough orientationClass 9: data should always be rejected

(Foken et al., 2004; Foken and Wichura, 1996)




Accuracy of surface fluxes

Eddy-covariance measurements according to recent findings (EBEX-2000 in USA and LITFASS-2003 in Germany)

Sonic anemometer

quality class sensible heat flux latent heat flux

Type A,e.g. CSAT3

1-3 5% or 10 Wm-2 10% or 20 Wm-2

4-6 10% or 20 Wm-2 15% or 30 Wm-2

Type B,e.g. USA-1

1-3 10% or 20 Wm-2 15% or 30 Wm-2

4-6 15% or 30 Wm-2 20% or 40 Wm-2

Foken and Oncley (1995), Mauder et al. (2006)




-500

-400

-300

-200

-100

0

100

200

0 3 6 9 12 15 18 21 24UTC

ener

gy

in W

m-2

Sensible heat flux

Latent heat flux

Net radiation

Ground heat flux

Residual

Energy balance closure problem

Foken and Oncley (1995), Mauder et al. (2006), Oncley et al. (2007), Mauder and Foken (2006), Foken (2008)




-500

-400

-300

-200

-100

0

100

200

0 3 6 9 12 15 18 21 24UTC

ener

gy

in W

m-2

Sensible heat flux

Latent heat flux

Net radiation

Ground heat flux

Residual

Energy Balance Closure Problem

Foken and Oncley (1995), Mauder et al. (2006), Oncley et al. (2007), Mauder and Foken (2006), Foken (2008)

WHAT IS TO DO BY THE USER?

Distribute the residual according to the Bowen ratioto the sensible and latent heat flux




Stull (1988)

Internal Boundary Layers




• Internal boundary layers

• Flagging scheme for each 30 min flux value in the NetCDF-file

Condition Flag value Description

0az with x3.00 0 Measurement within new

equilibrium layer

10 az

with x3.00 and x5.01 1 Disturbance range

1az with x5.01 2 Measurement above new

equilibrium layer

Internal boundary layers

0

1

2




Footprint analysis

• Combination of the flux quality approach with a forward Lagrangian footprint model(Göckede et al., 2004, 2006; Foken et al., 2004; Rannik at al., 2003)

Spatial representativeness

(footprint climatology)

Spatial distribution of

quality flags




Internal boundary layer evaluation:Height of internal boundary layer

Footprint analysis: Flux contribution from the target land use

Turbulence data quality (II)




Supplementary FOOT file

• 6 pictures per station:– Land use information map (on which

your footprint analysis is based on):

– Footprint climatology:

– Spatial distribution of quality flags in relation to footprint climatology

for u*, QH, QE, CO2:




WDCC data base structure

• Each station comprises 2 data sets:

• And 1 supplementaryfile (FOOT)Land use information map, footprint analysis

• Additional information possible (e.g. TK2 manual, references …)

Meteorological (MET): Radiation and soil measurements

Flux data set (FLUX): Turbulent fluxes, footprint analysis, IBL

NEBT

UF1ETG

IMK1ETG

IMK2ETG

IMK3ETG

MF1ETG

MF2ETG

MF3ETG

UBT1ETG

UBT2T

UBT3ETG

UBT4ETG

UBN1ETG

UV1EG

IMK4T

IMK5T

IMK6T

IMK7T

IMK8T

MET

FLUX

FOOT

d

d

s

::

::

::

::

cops

cops_<EXP(4)>_<INSTRU (6)>_<PARA(6)>_ <FLAG(1)>




Conclusion

We will write a cook book for the user.




Thank you for your attention !

quality controlled data base of the cops surface energy balance network

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