Eddy Covariance Measurement of
Turbulent Fluxes at the Land
Surface in Tropical Wet and Dry
Climate at Ile-Ife, Nigeria.
‘Gbenga Jegede
Department of Physics,
Obafemi Awolowo University,
Ile-Ife, Nigeria.
Colloquium “Perspectives in Micrometeorology”
Thurnau, Germany. 6th June, 2014.
Eddy Covariance Measurement of
Turbulent Fluxes at the Land
Surface in Tropical Wet and Dry
Climate at Ile-Ife, Nigeria.
A personal tribute to
Prof. Dr. Thomas Foken
.
“Perspectives in Micrometeorology”
Foken:
“…. seeks to give the practical user directly
applicable calculating and measuring methods
and also provides the basics for further
research”
Preface in “Micrometeorology” – Foken (2008), Springer-Verlag.
UBT (Nov., 2004)
Prof. Foken’s support for:
• Research
• Instrumentation
• Scholarship
in Micrometeorology Studies (eddy covariance measurements) at OAU, Nigeria.
Research Cooperation (with Prof. Foken)
1996-1998:
 DWD, Lindenberg (LINEX-96, 97)
Phase 1 - Germany
 UBT, Bayreuth
1998 – 2004:
 OAU, Ile-Ife (BREB, MBR) - SEBFEX
2004 – to date:
 OAU, Ile-Ife (EC method) - NIMEX
Phase 2 - Nigeria
Micrometeorological Studies @ OAU
• Characteristics of the SL turbulence intensity
• Effects of clouds on solar/net radiation
intensity
• Soil thermal properties (sfc albedo)
• Determination of sensible heat from soil sfc T
• Bowen ratio energy balance (BREB) &
Modified-BREB (MBR)
• Investigation of the surface energy balance
(EC method)
Studying exchanges (turbulent fluxes) of mass, momentum
and energy between the atmosphere and the earth’s
surface including the sub-surface medium.
Determination of Sfc. Energy fluxes
• Indirect methods
- Gradient or bulk technique
- flux-profile technique
• Direct methods
- Eddy Covariance technique
- Eddy accumulation technique
- Scintillometric technique
NIMEX: Nigeria Micrometeorological Experiments
(Beginning from Feb. 2004)
Aims:
 Acquisition of instrumentation for micrometeorological research
 Investigation of local/regional scientific
problems
 Human capacity building
 Validation of empirical relationships
Micrometeorology Lab
NIMEX Site, Ile-Ife (7.5oN, 4.5oE)
Micromet Research Facilities @ OAU, Nigeria
Sonic Anemometer (USA-1, CSAT3)
Infrared Gas Analyser (LI-7500)
Krypton hygrometer (KH20)
Acoustic Sounder (METEK PCS.2000)
Campbell Dataloggers (CR10X, CR1000)
Cup anemometers, psychrometers, soil heat flux
plates, soil thermometers, net radiometers, etc)
• Desktops & laptop computers
• Software (Loggernet, TK2)
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Profile measurements
Wind speed profiles
& direction
Psy. Air Temp. &
Surf. Temp. profiles
Data Acquisition
CR1000
Data downloaded to
PC
Soil Temp. & Moisture.
Soil Heat Flux (depths)
(February, 2010)
Looking to the west from the mast position
Looking to the east from the mast position
15-m mast for the profile
measurements
Solar & Atmospheric radiation
Net Radiometer
NR01/CNR1.
Net Radiometer
NR-LITE
Data Acquisition
CR10X
Pyranometer
CS300
PAR (Li-COR Quantum
Sensor) LI190SB
Data downloaded
to PC
Eddy Covariance (EC) System
Sonic Anemometer
(CSAT3)
Infrared Gas
Analyzer (LI-7500)
DataLogger
CR1000/Minilaptop PC
Temperature/
Humidity sensor
(HMP45C)
Sampling Rate: 10 - 20 Hz (selectable)
Storage: 1. Raw turbulent data
2. 30-min. averages of the covariances (fluxes)
Krypton
Hygrometer, KH20
Eddy Covariance (EC) Measurements
of turbulent fluxes at the NIMEX Site.
Dry season (Nov. – Mar.)
Wet season (Nov. – Mar.)
ca. 2013
ca. 2004
NIMEX Datasets
• Mean profile measurements:
wind direction, θ (15.0m)
wind speed, u (0.5, 1, 2, 4, 6, 8, 10, 15 m)
Air Temperature, T (0.5, 2, 4,10 m)
Surface temperature: Ts
Soil temperature, Ts (0.05, 0.10 & 0.30 m)
Soil heat flux, Hf (0.05, 0.1 & 0.3 m)
Global & net radiation: G, RN
(all data are stored as 1 min./10 min. averages)
• Eddy covariance (EC) measurements: u’, v’, w’, T’, a’ (16 Hz)
• Synoptic observations (Cloudiness)
Mar. 1 – 8, 2004
Jun. 10 - 13, 2010
Source: Ayoola & Jegede (2013).
Thank you for listening