Data Set Documentation (1)
1.TITLE
1.1 DATASET IDENTIFICATION
Fallow Bush Automatic Weather Station and radiation data
1.4 Revision date of this document
1 October 1993
2.INVESTIGATORS
2.1
Principal Investigator
C.R. Lloyd
2.2
Title of investigation
Surface layer measurements in HAPEX-Sahel
2.3
Contacts
2.3.1
2.3.2
Name
Address
2.3.3 Tel:
2.3.4 E-mail:
2.3.5 Fax:
CONTACT1
C.R.Lloyd
Institute of Hydrology
Wallingford, England,
0491-838800
CRL@UK.AC.NWL.UA
0491-832256
CONTACT2
J.H.C.Gash
Institute of Hydrology
Wallingford, England
0491-838800
J.GASH@UK.AC.NWL.UA
0491-832256
2.4 Requested form of acknowledgement
Financial support provided by the NERC through its TIGER
(Terrestrial Initiative in Global
Environmental Research) programme, award number GST/91/III.1/1A.
Data acquired by C.R. Lloyd and J.H.C. Gash of the Institute of Hydrology
is gratefully acknowledged.
3 INTRODUCTION
3.1 Objective/Purpose
To provide point and areal measurements of radiation balance,
evaporation, sensible heat and
momentum flux from three complex vegetation covers.
3.2
Summary of parameters
Aspirated air and wet bulb temperature, wind speed, wind direction,
rainfall, net radiation,
reflected solar radiation and incoming solar radiation
3.3
Discussion
Measurements were made at the SS Fallow Site near Sadore within the
HAPEX-Sahel Grid
Square.
4. THEORY OF MEASUREMENTS
Contact C.R.Lloyd ,
J.H.C.Gash or Manufacturer
5. EQUIPMENT
5.1.1
Platform
All instruments with the exception of net radiation and reflected
solar radiation over
grass/herb ground area, were mounted on the Institute of Hydrology tower
at the heights detailed
in section 5.1.5. To minimise the effects of shadows and reflections
form the tower, the net radiometer
and reflected solarimeter were mounted on a boom extending 4-5 m to the
south of the tower.
5.1.3 Key Variables
Aspirated air temperature
Aspirated wet bulb temperature
Wind speed
Wind direction
rainfall
Net radiation over composite vegetation
Incoming shortwave radiation
Reflected solar over composite vegetation
5.1.4 Principles of operation
Contact C.R.Lloyd , J.H.C.Gash or manufacturer
5.1.5 Instrument Measurement Geometry
Height (m)
Air temperature
6.65
wet bulb temperature
6.65
Wind speed
7.21
Wind direction
7.39
rainfall
0.35
Net radiation over vegetation4.67
Incoming shortwave radiation7.61
Reflected solar over vegetation4.56
5.1.6
Manufacturer of instrument
AWS
T-dry
T-wet
Wind dirn
Wind Speed
Rainfall
Net radiation
Incoming solar
Reflected solar
5.2
Didcot Instrument Company, Abingdon, Uk
Campbell Scientific, Loughborough,UK
Campbell Scientific, Loughborough,UK
Didcot Instrument Company, Abingdon, UK
"
"
"
Rimco, Australia
Radiation Energy Balance Systems, Seattle, USA
Kipp and Zonen, Delft, The Netherlands
"
"
"
"
"
"
Calibration
Contact C.R.Lloyd ,
J.H.C.Gash or Manufacturer
5.2.1 Specifications
T-dry
Thermistor
T-wet
Thermistor
Wind dirn
16 Magnetic reed closures
Wind speed magnetic contact closures
Rainfall
203mm diameter orifice : 0.5mm tipping bucket
mechanism, magnetic contact
sensing
Net radiationdual hemisphere single polythene dome Q*5 net
radiometers
Incoming solarDual glass dome CM5
Relected solarDual glass dome CM5
5.2.1.1 Tolerance
T-dry,T-wet: typically better than 0.2 deg.C
Wind direction resolution = 1/16 of a circle on individual
measurements
Windspeed subject to stalling below 0.6 m/s
Rainfall measurement resolution = 0.5mm
Net radiation measurements accurate to 4-7 W/m**2
Incoming and reflected solar: accurate to 1%: response time is
99% in 30 sec.
5.2.3 Other calibration information
6. Procedure
6.1 Data Acquisition
Data is recorded using a dedicated Campbell Logger CR10
6.2 Spatial Characteristics
6.2.1 Spatial coverage
Climate variables dependent on wind direction, stability and height
i.e. WAB dependent
Radiation measurements are whole hemisphere measurements with
maximum weight normal
to the sensor surface
6.2.2 Spatial resolution
WAB or hemispherical integrals
6.3
Temporal Characteristics
6.3.1 Temporal coverage
Continuous measurements throughout the SOP
Data available from day 230 to day 284
6.3.2 Temporal resolution
10-minute intervals
7. OBSERVATIONS
7.1 Field notes
8. DATA DESCRIPTION
8.2 Type of data
The data consists of ten-minute averaged logged measurements of wet bulb
temperature, dry bulb
temperature, wind speed, wind direction, rainfall, net radiation,
incoming solar radiation and reflected
solar radiation. These data are stored as a plain ASCII file, each line
giving measurements at a certain
time, with each variable separated by a number of blanks.
--------------------------------------------------------------------8.2.1
8.2.2
8.2.3
8.2.4
--------------------------------------------------------------------day of year
--------------------------------------------------------------------Time
--------------------------------------------------------------------Tw
Wet bulb temperaturemin =0
Degrees Celsius
max =50
missing = .
--------------------------------------------------------------------Td
dry bulb temperaturemin =0
Degrees Celsius
max = 50
missing = .
--------------------------------------------------------------------Ws
Wind speed
min = 0
metres per sec
max = 10
missing = .
--------------------------------------------------------------------Wd
Wind directionmin =0
degrees magnetic
max = 360
missing = .
--------------------------------------------------------------------Ppt
Rainfall
(bare soil)
min =0
mm
max = 50
missing = .
--------------------------------------------------------------------rnv
(W/m**2)
Net radiation over min =-100
Watts per square metre
vegetation
max = 900
missing = .
--------------------------------------------------------------------Si
incoming shortwave min =-100
W/ m**2
radiation
max =1000
missing = .
--------------------------------------------------------------------Srv
reflected solar radiation min =-100W/ m**2
max = 600
missing = .
---------------------------------------------------------------------
8.3 Sample database record
267
13:00 23.05 26.1 2.1 49.1 3.5 222.5
509.3 213.5
8.4 Data format
9. DATA MANIPULATION
10. ERRORS
10.2 Data Validation by Source
The incoming solar radiation measurements were compared to those made by
the Institute of
Hydrology at the two SS sites (millet and tiger bush).
Wet and dry bulb temperatures were compared and are indicated by missing
values if both
measurements are the same (this indicates drying out of the wick on the
wet bulb thermometer)
11. NOTEs
12. REFERENCES
12.2 Journal Articles and Study Reports
Ground Station Documentation
1.
1.1
INVESTIGATOR
C.R. Lloyd
1.2.1
1.2.2
1.3
C.R. Lloyd
J.H.C.Gash
03/04/93
1. Air and wet bulb temperature, wind speed, wind direction, rainfall net
radiation, reflected solar
radiation and incoming solar radiation .
2. STATION IDENTIFICATION AND LOCATION
2.1
Southern Supersite Fallow
Bush.
Nearest village=Sadore
2.2 Station Code
SS
2.3 Latitude
13 14.63'
2.4 Longitude
2 14.65'
2.5
Altitude
250m
2.6 Super Site and WAB
SS
3. Data Acquisition
Measurements were made at the SS Fallow Site near Sadore within the
HAPEX-Sahel Grid
Square.