advective effects on short term and long term net ecosystem exchange
DESCRIPTION
Advective effects on short term and long term Net Ecosystem Exchange C. Feigenwinter 1 , C. Bernhofer 2 , R. Vogt 1 , T. Grünwald 2 , U. Eichelmann 2 , H. Prasse 2 , U. Postel 2 1 University of Basel, Institute of meteorology, climatology and remote sensing - PowerPoint PPT PresentationTRANSCRIPT
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