thermometer variable: temperature units: degrees celsius ( o c) accuracy: marked to 0.5 o c cost:...
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Thermometer
• Variable: temperature• Units: Degrees Celsius (oC)• Accuracy: marked to 0.5 oC• Cost: £10• Site: in the shade (e.g. a
Stevenson Screen)• Mercury (or sometimes
coloured alcohol) in the bulb expands and contracts up the calibrated tube with changes in the ambient air temperature
Max & Min Thermometer
• Details as for thermometer, except an index marker is pushed up or down by the tube of mercury to indicate the maximum or minimum
Whirling hygrometer
• Variables: temperature and wet bulb temperature
• Units: Kelvin or Degrees Celsius
• Accuracy: marked to 0.5 oC (range -5 to +50 oC)
• Cost: £45• Site: in the shade• Whirl it round your head so the
thermometer bulbs are well ventilated and there is sufficient evaporation from the wet bulb to achieve lowest possible temperature.
Assman psychrometer
• Similar to the whirling hygrometer, but uses a wind up fan to ventilated the dry and wet bulb thermometers.
Humidity slide rule
• Variable: converts between water vapour content measures
• Units: n/a• Accuracy: ~1 %• Cost: cheap!• Site: n/a• A ready-reckoner for
conversion between, e.g. wet bulb temperature and relative humidity
Barograph (recording Barometer)
• Variable: atmospheric pressure
• Units: millibars (mb) or Pascals (Pa)
• Accuracy: ~0.1 mb• Cost: ?• Site: Anywhere• An aneroid barometer contains
a partial vacuum in the sealed metal aneroid cell, hence changes in pressure are amplified by movements of the arm attached to the cell.
Net radiometer
• Variables: upwelling and downwelling radiation
• Units: W m-2
• Accuracy: ?• Cost: ?• Site: Exposed site without
shading• Dark surfaces absorb
longwave or shortwave radiation, causing a change in voltage which can be measured electronically and converted to radiation.
Dome solarimeter
• Variable: solar radiation• Units: W m-2
• Accuracy: ?• Cost: ?• Site: exposed• As for net radiometers
Tipping bucket raingauge
• Variable: rain rate and amount• Units: mm• Accuracy: 0.2 mm• Cost: £300-£700• Site: exposed horizontal
location• Rain falls into cone and tips a
small bucket once full, with that time recorded, thus a rain rate can be observed. Cone amplifies signal.
Air meter
• Variable: the “run of air” & hence wind speed
• Units: m & m s-1
• Accuracy: dependent on the observation time
• Cost: no longer available.• Site: away from buildings, etc• Impeller spun round by the
wind, turning dials to measure the wind run.
Handheld anenometer
• Variable: wind speed (instantaneous)
• Units: m s-1 or equivalent• Accuracy: poor.• Cost: cheap• Site: handheld• Wind blows the cups around to
give an instantaneous reading.
Sodar (Acoustic Radar)
• Variable: Backscatter• Units: amplitude• Accuracy: ?• Site: away from buildings,
people, & noise!• Cost: ~£1000-10,000• Acoustic pulses are scattered
back to the receiver, from small-scale density changes (e.g. turbulence), with the volume and time-lag measured to give amplitude and range.
Sodar (Acoustic Radar)
• Variable: Backscatter• Units: amplitude• Accuracy: ?• Site: away from buildings,
people, & noise!• Cost: ~£1000-10,000• Acoustic pulses are scattered
back to the receiver, from small-scale density changes (e.g. turbulence), with the volume and time-lag measured to give amplitude and range.
Doppler sodar
• Variable: Backscatter & derived wind profiles
• Units: n/a and m/s• Accuracy: ~1 m/s• Site: remote!• Cost: £10,000• Acoustic beams fired in
several directions, so scatters relative movement can be determined, and hence wind speed & direction in 3D.
Doppler sodar
• Variable: Backscatter & derived wind profiles
• Units: n/a and m/s• Accuracy: ~1 m/s• Site: remote!• Cost: £10,000• Acoustic beams fired in
several directions, so scatters relative movement can be determined, and hence wind speed & direction in 3D.
Radiosonde (Upper air sounding)
• Variables: an atmospheric sounding (i.e. vertical profile) of, typically, pressure, temperature, relative humidity & wind •Units: various•Accuracy: various•Cost: £100 per sonde •Site: away from buildings, good spatial representation, often airports•Balloon is filled with Helium gas and released rising up few metres per second, the radiosonde measures and transmits data to a ground station
Radiosonde (Upper air sounding)
• Variables: an atmospheric sounding (i.e. vertical profile) of, typically, pressure, temperature, relative humidity & wind•Units: various•Accuracy: various•Cost: £100 per sonde •Site: away from buildings, good spatial representation, often airports•Balloon is filled with Helium gas and released rising up few metres per second, the radiosonde measures and transmits data to a ground station
Radar• Variables: Backscatter, usually
from hydrometeors, such as rain drops, hail, snow, etc.
• Units: backscatter amplitude• Accuracy: ?• Site: away from buildings,
good spatial distribution• Cost: £10,000-£1millions• Radio waves emitted and
reflected back, with return amplitude and time-lag giving backscatter intensity and range. These can be related to precipitation intensity.
• Doppler radars also available.
Radar• Variables: Backscatter, usually
from hydrometeors, such as rain drops, hail, snow, etc.
• Units: backscatter amplitude• Accuracy: ?• Site: away from buildings,
good spatial distribution• Cost: £10,000-£1millions• Radio waves emitted and
reflected back, with return amplitude and time-lag giving backscatter intensity and range. These can be related to precipitation intensity.
• Doppler radars also available.
Radar• Variables: Backscatter, usually
from hydrometeors, such as rain drops, hail, snow, etc.
• Units: backscatter amplitude• Accuracy: ?• Site: away from buildings,
good spatial distribution• Cost: £10,000-£1millions• Radio waves emitted and
reflected back, with return amplitude and time-lag giving backscatter intensity and range. These can be related to precipitation intensity.
• Doppler radars also available.
Satellites!• Variable: Radiation & derived
brightness temperature• Units: W & derived K• Resolution: down to < 1 km• Site: space! Either
geostationary or polar orbits• Cost: millions & millions• Passive satellites measure up-
welling radiation at various wavelengths (visible, infra red & microwave)
• Active satellites work more like radars.
Satellites!• Variable: Radiation & derived
brightness temperature• Units: W & derived K• Resolution: down to < 1 km• Site: space! Either
geostationary or polar orbits• Cost: millions & millions• Passive satellites measure up-
welling radiation at various wavelengths (visible, infra red & microwave)
• Active satellites work more like radars.
Satellites!• Variable: Radiation & derived
brightness temperature• Units: W & derived K• Resolution: down to < 1 km• Site: space! Either
geostationary or polar orbits• Cost: millions & millions• Passive satellites measure up-
welling radiation at various wavelengths (visible, infra red & microwave)
• Active satellites work more like radars.
Observing scenarios:
• You have been tasked with determining the structure & governing physics of the wind field over Greenland – discuss in groups how to achieve this challenge.