advective effects on short term and long term net ecosystem exchange

Advective effects on short term and long term Net Ecosystem Exchange

C. Feigenwinter1, C. Bernhofer2, R. Vogt1 ,T. Grünwald2, U. Eichelmann2, H. Prasse2, U. Postel2

1 University of Basel, Institute of meteorology, climatology and remote sensing2 TU-Dresden, Institute of hydrology and meteorology

MCR LabMeteorology – Climatology – Remote Sensing

University of Basel

Site overview

Results and conclusions MORE I

Experimental setup MORE II (More measurements in the ORE mountains)

Short theory and methodology

Results MORE II

effects of advective fluxes on NEE

Conclusions and outlook

Advective effects on short term and long term Net Ecosystem Exchange

C. Feigenwinter1, C. Bernhofer2, R. Vogt1 ,T. Grünwald2, U. Eichelmann2, H. Prasse2, U. Postel2

1 University of Basel, Institute of meteorology, climatology and remote sensing2 TU-Dresden, Institute of hydrology and meteorology

Overview

Overview anchor station Tharandter Wald

Elevation

Inclination

Landuse

Exposition

50°58‘ N, 13°34‘ E

375 m a.s.l.

Annual mean temp. 7.7°

Annual mean precip. 819 mm

Site overview

[g C m-2 d-1][g C m-2 period-1]

00:00-08:00

08:00-16:00

16:00-24:00

Total day

horizontal advection

-1.78 0.80 -1.25 -2.23

vertical advection

1.52 -0.20 1.19 2.51

storage change

-0.08 -0.19 0.27 0.00

EC flux 0.73 -3.00 0.43 -1.84

Total 0.39 -2.59 0.64 -1.56

Results from MORE I (2001, DOY 263-283)(Feigenwinter et al., 2004, Boundary-Layer Meteorol., in press)

----- EC + storage change

+ advection terms

difference: 0.18 g C m-2 d-1 (10 %)

MORE I

Methododical problems and deficits for evaluation of the advection terms (i.e. vertical profiles of wind velocity, CO2 concentrations and horizontal concentration gradients are strongly dependent on the experimental design)

Short duration of the MORE I experiment does not allow conclusions that are generally valid. Results have to be confirmed and/or adjusted by long term measurements.

Results published in:Feigenwinter, C., Bernhofer, C. and Vogt, R. (2004): The influence of advection on the short term CO2 budget in and above a forest canopy, Boundary-Layer Meteorology, in press.

MORE II Long term study (growing season)

Experimental setup essentially improvedOptimised coordination between measurements (gradients, wind profile, sampling rates)

Adaptation of the permanent measurements according to the task

Conclusions from MORE I

MORE I

Experimental setupsituation

Experimental setup: Situation

MORE I : Sep/Oct 2001

height (trees) 26 m (P2, P3)

MORE II: Mai/Oct 2003

height (towers) 30 m (P1, P2, P3)

P1

P2

P3

P2

P3

N

0 m 50 m50 m

ASTW 42 m

18.0 m

8.0 m

2.0 m

0.5 m

37.0 mq,CO2

u',v',w',T'T

q,CO2

q,CO2

42.0 mu',v',w',T',q',CO2'

q,CO2

u',v',w',T'T

q,CO2

u',v',w',T'T, 2 x u,v 33.0 m

26.0 m

q,CO2

T, 2 x u,v

q,CO2

T, 2 x u,v

q,CO2

T, 2 x u,v

q,CO2

T, 2 x u,v

q,CO2

T

0.2 mq,CO2

T

ASTWanchorstation

20.0 m

8.0 m

2.0 m

0.5 m

2.5 m

q,CO2

30.0 m q,CO2

u',v',w',T'

u',v',w',T'

T

T

q,CO2

q,CO2

q,CO2

q,CO2

P3

20.0 m

8.0 m

2.0 m

0.5 m

2.5 m

q,CO2

30.0 mq,CO2

u',v',w',T'

u',v',w',T'

T

T

q,CO2

q,CO2

q,CO2

q,CO2

P2

20.0 m

8.0 m

2.0 m

0.5 m

2.5 m

q,CO2

30.0 mq,CO2

u',v',w',T'

u',v',w',T'

T

T

q,CO2

q,CO2

q,CO2

q,CO2

P1

CR10 data loggerAM25T MUXSMD-INT8

Gas-Multiplexerand IRGA

(LiCor 6262)

Gas-Multiplexerand IRGA

(LiCor 6262)

IRGA andEdiSol

data acquisition

PIP6Labview sonic

data acquisition

Experimental setup MORE II

Gas-Multiplexerand IRGA

(LiCor 6262)

Experimental setup: Instrumentation

Experimental setup: Tower P1

Experimental setup: Tower P2

Experimental setup: Tower P3

NEEdzztSrz

0

),( rz

dzt

zc

0

)( )('' rzcw

rz

dzz

zczw

0

)()(

rz

dzy

zczv

x

zczu

0

)()(

)()(

I source/sink of c

II storage change

III turbulent flux(EUROFLUX, Aubinet et al., 2000; FLUXNET, Agr. For. Met. Vol. 113, 2002)

IV vertical advection(Lee, 1998; Baldocchi, 2000)

V horizontal advection(Aubinet et al., 2003, Staebler and Fitz-jarrald, 2004; Feigenwinter et al., 2004)

x

y

z

Experimental evaluation of CO2 exchange in a forest ecosystem

Theory und methodologynon turbulent advection terms

rz

dzz

zczw

0

)()(

rz

dzy

zczv

x

zczu

0

)()(

)()(

ccwdzz

zczw rr

r

zz

z

0

)()(

vertical advection

Theory and methodology

Estimation of the mean vertical wind component:

sinusoidal fit over a sufficiently long period(Lee, 1998; Baldocchi et al., 2000; Paw U et al. (2000))

or „planar fit“ (Wilczak et al., 2001)

)sin(tan 210

22aaavuww

rrrr zzmeasuredzz

Theory und methodologynon turbulent advection terms

rz

dzz

zczw

0

)()(

rz

dzy

zczv

x

zczu

0

)()(

)()(

ccwdzz

zczw rr

r

zz

z

0

)()(

vertical advection

Theory and methodology

Estimation of the mean CO2 concentration in the volume below the reference level:

and log-square fit of the concentration profiles

rz

r

dzzcz

c0

)(1

● tower P1 (30 m)

● tower P2 (30 m)

● tower P3 (30 m)

● main tower (anchor station)

Theory und methodologynon turbulent advection terms

rz

dzz

zczw

0

)()(

rz

dzy

zczv

x

zczu

0

)()(

)()(

rz

dzy

zczv

x

zczu

0

)()(

)()(

horizontal advection

Theory and methodology

___ measured gradient

__ sonics

__ cup anemometer

Resultsnon turbulent advection terms

rz

dzz

zczw

0

)()(

rz

dzy

zczv

x

zczu

0

)()(

)()(

ccwdzz

zczw rr

r

zz

z

0

)()(

vertical advection

Results MORE II

positive during nighttime with large scatterzero during daytime

Theory und methodologynon turbulent advection terms

rz

dzz

zczw

0

)()(

rz

dzy

zczv

x

zczu

0

)()(

)()(

rz

dzy

zczv

x

zczu

0

)()(

)()(

horizontal advectionFlow conditions during MORE II (DOY 155-285)

- mainly from SW – W – NW

- no distinct drainage flow at night

Results MORE II

Theory und methodologynon turbulent advection terms

rz

dzz

zczw

0

)()(

rz

dzy

zczv

x

zczu

0

)()(

)()(

rz

dzy

zczv

x

zczu

0

)()(

)()(

horizontal advectionDistribution of horizontal concentration gradients during MORE II (DOY 155-285)

- large in the lower trunk space at night

- main direction NE – E - SE

Results MORE II

Theory und methodologynon turbulent advection terms

rz

dzz

zczw

0

)()(

rz

dzy

zczv

x

zczu

0

)()(

)()(

rz

dzy

zczv

x

zczu

0

)()(

)()(

horizontal advectionHorizontal advection MORE II (DOY 155-285)

- large in the lower trunk space at night, large scatter

- positive (source term)!

- zero during daytime

Results MORE II

Fluxes for a layer thickness of 1 m at the resp. height

0.5 m

2.0 m

8.0 m

20.0 m

30.0 m

Theory und methodologynon turbulent advection terms

rz

dzz

zczw

0

)()(

rz

dzy

zczv

x

zczu

0

)()(

)()(

rz

dzy

zczv

x

zczu

0

)()(

)()(

horizontal advectionHorizontal advection MORE II (DOY 155-285)

- large in the lower trunk space at night

- positive (source term)!

- small during daytime

Results MORE II

Conclusions and outlookConclusions and outlook

Vertical and horizontal advection are in the same order of magnitude as the turbulent EC-flux of CO2

The large scatter of the mean advection terms is the result of a large day to day variability

Including the advection terms into the NEE equation significantly increases the nightly CO2 source and thus reduces the Carbon sink of the forest

There are still many methododical problems and only a few studies for comparison. The presented results may therefore only be characterisic for the specific site