Microclimatological Instrumentation
Trent Weather
Station (Lafleur)
Lethbridge Microclimate Station (Flanagan)
Example of
Coulee Weather
Station
(Letts)
Tipping Bucket Raingauge
Each ‘tip’ is logged by
the datalogger
Tipping
Bucket
Raingauge
Mechanism
Old Fashioned Raingauge
Parque Munchique
Cauca, Colombia
Lakeview
Ridge,
Waterton Lakes
National Park
Temperature Measurement
Thermocouple
2 wires of different composition joined by an electrical source
Electrical resistance sensitive to temperature
Resistance is measured and coverted to temperature information
Thermister
The hotter it gets, the less power it lets through
Resistance is measured and converted to temperature information
Temperature and Relative Humidity
Temperature and RH sensors
housed in Gill Radiation Shield
Relative humidity sensor
detects vapour adsorption onto
a sulfonated polystyrene surface
Temperature Sensor:
thermister
Function of Shields:
Protect sensor from radiation (especially incoming shortwave and
outgoing longwave radiation) while allowing air to pass.
Stevenson Shield
An earlier radiation
shield often used
with wet and dry
bulb thermometers
Photo: Trent Weather Station
Rainfall and Snowfall Measurements
Precipitation Gauge with Nipher Shield
Wind Speed and Direction
Cup anemometer
signal frequency
converted
to windspeed
Wind vane
Sonic anemometer
Sound waves measure
wind speed and temperature
Time of flight for a sonic
impulse to travel from a
transmitting to a receiving
transducer in both directions
determines wind speed
and direction
Sonic
Transducers
Why is this
sonic anemometer
placed so much
higher than it
would be placed
over a grassland
or a peatland ?
Source: University of Colorado
(African savanna site)
Micrometeorological Tower
Yikes !
Radiation Measurements
Shields made of materials
appropriate for desired wavelength
(eg. polyethylene for net radiation
– transparent to both longwave
and shortwave energy)
Net radiometer
Millivolt signals are
proportional to the
radiation level
Pyranometer
Measures solar radiation on
planar surface
Pyrgeometer
Measures infrared (longwave)
radiation
UV-B Radiometer
Measures ultraviolet solar radiation
on planar surface
Base camp
2º30´25´´N, 77º00´02´´W, 1450 m
Field Station
Tambito al
Cocal River
Photo taken from
microclimate station
Juntas,
El Tambo,
Cauca,
Colombia
901 m asl
Radiation Measurements
L
K
UV-A
K (not visible)
L
Also: pyranometer for broadband incoming radiation
0
08h00
Radiation Data
10h00
12h00
14h00
16h00
14h00
16h00
Solar Time
b)
Photosynthetically active radiation
(µmol m-2 s-1)
1600
1200
800
400
0
08h00
10h00
12h00
Solar Time
More radiation sensors…
Source: University of Colorado
Diffuse Radiation
Measured using a
shade disk
Radiation from entire
sky except from within
3 of Sun
Heat Flux Plate
Senses conductive heat
transmission in the medium
within which it is buried
Used for soil energy
balance studies
Voltage proportional
to heat flux through
plate
Sensible and Latent Heat Fluxes
Eddy correlation (later)
•Sonic anemometer
measurements of vertical
velocity and temperature
•Krypton hygrometer
measurements of water
vapour density
Krypton Hygrometer
Source emits in the 121-122
nm range for which absorption
by water vapour is strong and
other gases do not absorb
Detector senses amount of
radiation received in
this range
Baseline established by
conventional measurements
Photosynthesis Measurements
Weather stations often support
ecological or biological research
“Leaf’ Wetness Sensor
Leaf Wetness Data
1
0, 9
0, 8
Proportional
leaf
0, 7
wetness
0, 6
2.5 m etre s
0, 5
5.0 m etre s
10 m etre s
0, 4
0, 3
0, 2
0, 1
0
0
2
4
6
8
10
12
Hour
14
16
18
20
22
1
0,9
Figure 5.11a Average leaf wetness at 2.5, 5.0 and 10m height within the canopy
of the Bosque station.
0,8
Proportional
leaf
0,7
wetness
2.5 metres
5.0 metres
10 metres
0,6
0,5
0,4
0,3
0,2
0,1
0
9 Aug
0
19 Aug
200
400
Day
29 Aug
600
7 Sept
Downloading data from the datalogger…
Ideally, this is how it’s
supposed to look…
Nice and organized !
Power Supplies
Equipment Rack
Closed Path IRGAS
(later)
Calibration
Equipment
Source: Dr. Larry Flanagan
Data Acquisition Computer
Other fieldwork related problems…
… turned out to be a ‘false’ Coral (phew!)
Still to come:
•CO2/H2O Analyzer
Measures CO2 and H2O fluxes
using eddy covariance techniques
Why ? To measure carbon balance