FUT., Akure Carbon, water and energy fluxes in a West African humid tropical ecosystem 1,3 Balogun A.A., 1,3 Balogun I.A, 1,3 Oladosu O.R., 2,3 Jegede O.O. 1 Federal University of Technology, Akure, Nigeria 2 Obafemi Awolowo University, Ile-Ife, Nigeria 3Atmospheric Research Group (ARG), Nigeria CarboAfrica Conference, Pointe Noire, Congo 17 – 19, March 2010
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FUT., Akure Carbon, water and energy fluxes in a West ... · FUT., Akure Introduction •NlMEX is an on-going collaborative research project between the Atmospheric Research Group
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FUT., Akure
Carbon, water and energy fluxes in a West African humid tropical ecosystem
•With similar results that differ slightly from the generality in the literature for σw/u* & σq/q*
FUT., Akure
St. Paul, MN, USA
Ile-Ife, Nigeria
FUT., Akure
Though both sites are at different geographic/climatic
locations, the data sets reported here were for a
period of high temperatures and progressive soil
moisture depletion at both locations.
0
5
10
15
20
25
54 56 58 60 62 64 66 68
Time (DOY)
Pre
cip
itati
on
(m
m)
0
5
10
15
20
Vo
lum
etr
ic S
oil
Mo
istu
re (
%)
Rainfall (mm)
SMC (%)
Top: Rainfall and soil
moisture content between
Feb19 – Mar9, 2004 at
Ile-Ife, Nigeria.
Bottom: Rainfall and soil
moisture content between
Jul19 – Jul 31, 2006 at
St. Paul, USA.0
5
10
15
20
25
199 201 203 205 207 209 211 213
Time (DOY)
Pre
cip
itati
on
(m
m)
0
5
10
15
20
25V
olu
metr
ic S
oil
Mo
istu
re (
%)
Rainfall (mm)
SMC (%)
FUT., Akure
Table after Thomas & Foken 2002
FUT., Akure
Parameterisations of Andreas et al., 1998
for -4 < ζ ≤ -0:1,
σw/u* = 1.20(0.70 - 3.0 ζ)1/3
for -1 ≤ ζ ≤ 0,
σw/u* = 1.20
for -1 ≤ ζ ≤ 0,
σw/u* = 1.20(1 – 0.2 ζ)
FUT., Akure
Parameterisations of Andreas et al., 1998
Vertical velocity
Temperature and humidity
For temperature, C = 3.2; for humidity, C = 4.1 Andreas, 1998.
FUT., Akure
Results: σw/u*
Near Neutral
Nigeria: z/L < ±0.05
USA: z/L < ±0.06
P77: 1.3, Panofsky et al., 1977
0
0.5
1
1.5
2
-0.06 -0.03 0 0.03 0.06
z/L
σw
/u* Nigeria
USA
P77
FUT., Akure
σw/u*
Unstable
0
1
2
3
4
0 0.5 1
-z/L
σw
/u*
Nigeria
USA
P77
A98w
A98w: Andreas et al., 1998
P77: Panofsky et al., 1977
Not significantly different from Panofsky and Dutton, 1984
FUT., Akure
σw/u*
Stable
Bal: 1.3*(1+(0.25*z/L)), Balogun et al., 2009
0
0.5
1
1.5
2
2.5
0 1 2
z/L
σw
/u* Nigeria
USA
z/LA98
P77
Bal
FUT., Akure
Results: σT/T*
Near Neutral
0
5
10
-0.1 0 0.1
z/L
σT/T
*
Nigeria
USA
ThF91
ThF91
ThF91: Foken et al., 1991
see Table 1 for z/L ranges
FUT., Akure
Results: σT/T*
Stable
0
5
10
0 0.1 0.2 0.3 0.4 0.5
z/L
σT/T
*
Nigeria
USA
ThF91
A98
A98: Andreas et al., 1998
ThF91: Foken et al., 1991
FUT., Akure
Results: σT/T*
Unstable
0
5
10
-2 -1 0
z/L
σT/T
*
Nigeria
USA
ThF91
A98
A98: Andreas et al., 1998
Wyg71: Wyngaard et al, 1971
ThF91: Foken et al., 1991
In good agreement with Wyngaard et al, 1971
0.1
1
10
100
0.001 0.1 10
-z/L
σT/T
* Nigeria
USA
Wyg71
ThF91
A98
FUT., Akure
Results: σq/q*
-1/3 law obeyed but with a coefficient of 0.85
0
5
10
-2 -1 0
z/L
σq
/q*
Nigeria
USA
A98
Wyg71
z/L95
z/L85
0.1
1
10
100
0.001 0.1 10
-z/Lσ
q/q
*
Nigeria
USA
z/L85
Hog74
z/L95
A98b
FUT., Akure
Conclusions
• Remarkable similarity/agreement in the flux-variance relationships at both sites for w, T & q.
•MO similarity appears to be obeyed at both locations.
•Panofsky et al., 1977 parameterization fits the w flux-variance relationship best for near neutral and unstable conditions at both sites.
• A new parameterization for w, 1.3*(1+(0.25*z/L)), Balogun et al., 2009 under stable conditions fit the data at both sites better than existing parameterizations for the prevailing atmospheric & soil conditions
•The parameterization of Foken et al.,1991 best fitted T for near neutral
and stable conditions.
•While those of Andreas et al., 1998, Wyngaard et al, 1971& Foken et al., 1991 were in good agreement for T for –z/L < -0.05.
FUT., Akure
Conclusions Cont’
Conclusions Cont’d
•Though (z/L)-1/3 law was obeyed for q, but with a coefficient
of 0.85 which is lower than the 0.95 – 1 for T at both sites. This differ from most published results where the flux-variance
similarity functions for q are consistently larger in magnitude
than their T counterpart (Katul & Hsieh, 1995; Lamaud & Irvine, 2006).
•The high temperatures and water stress may have been
responsible for this. Data analysis is still ongoing to confirm this suggestion and find other possible causes.
FUT., Akure
Note for CarboAfrica Secretariat;
• We have a vibrant & active Micrometeorology/ARG that would be happy to collaborate and participate in the next
phase of the CarboAfrica project.
• How can we have access to the CarboAfrica flux datasets
FUT., Akure
Acknowlegement
•The authors acknowledge funding for NIMEX-1 from IPPS,
DAAD, the University of Bayreuth, Germany, The University of Minnesota, USA, the Obafemi Awolowo University, Ile-Ife,
Nigeria and the Federal University of Technology, Akure, Nigeria.
•The efforts of colleagues from all participating institutions are