FUT., Akure Carbon, water and energy fluxes in a West ... · FUT., Akure Introduction •NlMEX is...
Transcript of FUT., Akure Carbon, water and energy fluxes in a West ... · FUT., Akure Introduction •NlMEX is...
FUT., Akure
Carbon, water and energy fluxes in a West African humid tropical ecosystem
1,3Balogun A.A., 1,3Balogun I.A, 1,3Oladosu O.R., 2,3Jegede 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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Introduction
•NlMEX is an on-going collaborative research project between the Atmospheric Research Group (ARG), Nigeria and the University of
Bayreuth (UBT), Bayreuth in Germany with support from IPPS
Sweden.
•Initially designed to study the surface-atmosphere mass and
energy exchange processes at a humid tropical location.
•NIMEX-1 and NIMEX-2 have successfully been conducted in 2004
and 2005 respectively.
•Major results have been reported in the literature, also reviewed
here..
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Introduction Cont’d
•The ARG is now conducting NIMEX-3 between March and April, 2010.
• Aims to expand the scope of the earlier studies to include the monitoring of CO2 fluxes by EC system, using an ultrasonic anemometer (CSAT3) and
a gas analyser (LI-7500).
•NIMEX-3 measurements will complete the gaps that were apparent in NIMEX-1 and NIMEX-2 datasets.
•NIMEX-3 is a first attempt of CO2 flux monitoring in Nigeria, in order to quantify and understand ecosystem carbon, water and energy budgets.
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Nimex Site Location
Ile-Ife, Nigeria
Ile-Ife, Nigeria (7o 33’N, 4o 33’E): Agricultural fallow bush land.
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Site Layout & Instrumentation Ile-Ife, Nigeria
NIMEX is one of the few direct
measurements of all component of the
surface energy balance in tropical West
Africa.
•The measurements in 2004 & 2005, during
the transition from the dry to wet season
using;
•Metek USA-1 sonic: z = 2.48m
•Campbell KH-20 hygrometer: z = 2.48m
•Wind, temperature & humidity profiles
•Soil heat flux, temperature and moisture.
•Precipitation
•IRT surface temperature
Site Picture from Mauder et al., 2007
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Site Layout & InstrumentationSt. Paul, USA
Nimex3-2010;
CSI, Csat3 Sonic
Li-cor LI-7500 CO2
& H20 IRGA
Suburban turf
grass site in St Paul, MN, USA
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Volumetric soil moisture and precipitation aggregated to 30 minutes during NIMEX-1 in Ile-Ife, Nigeria (Mauder et al 2007)
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Radiation balance components for three selected days (Mauder et al 2007)
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Energy balance components of the selected days during NIMEX-1 representing three different typical soil and weather conditions: (Mauder et al 2007)
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Surface energy balance closure during NIMEX-1
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Introduction
•Monin Obukhov similarity theory (MOST) provided the
theoretical foundation for present day understanding of boundarylayer meteorology.
•But, despite the success of MOST in unifying theory and
observations, uncertainties persists in some of the universal functions that it predicts should exist (Andreas et al., 1998).
•Parameterisations for the integral turbulence characteristics of
wind components, temperature and humidity (e.g. Foken et al.,
1991; Andreas et al., 1998; Hogstrom 1990; Panofsky et al., 1977; Wyngaard et al., 1971).
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Introduction
•Flux-variance relationships at two different locations:
•Ile-Ife, Nigeria (7o 33’N, 4o 33’E): Agricultural fallow bush land.
•St. Paul, Minnesota (44o 57’N, 94o 33’W): Suburban turf grass lawn.
•With similar results that differ slightly from the generality in the literature for σw/u* & σq/q*
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St. Paul, MN, USA
Ile-Ife, Nigeria
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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 (%)
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Table after Thomas & Foken 2002
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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)
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Parameterisations of Andreas et al., 1998
Vertical velocity
Temperature and humidity
For temperature, C = 3.2; for humidity, C = 4.1 Andreas, 1998.
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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
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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
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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
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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
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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
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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
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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
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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.
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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.
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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
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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
also acknowledged.
Thank You!