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Thermometer Variable: temperature Units: Degrees Celsius ( o C) Accuracy: marked to 0.5 o C Cost: £10 Site: in the shade (e.g. a Stevenson Screen) Mercury.

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Presentation on theme: "Thermometer Variable: temperature Units: Degrees Celsius ( o C) Accuracy: marked to 0.5 o C Cost: £10 Site: in the shade (e.g. a Stevenson Screen) Mercury."— Presentation transcript:

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2 Thermometer Variable: temperature Units: Degrees Celsius ( o C) Accuracy: marked to 0.5 o C 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

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4 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

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6 Whirling hygrometer Variables: temperature and wet bulb temperature Units: Kelvin or Degrees Celsius Accuracy: marked to 0.5 o C (range -5 to +50 o C) 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.

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8 Assman psychrometer Similar to the whirling hygrometer, but uses a wind up fan to ventilated the dry and wet bulb thermometers.

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10 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

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12 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.

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14 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.

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16 Dome solarimeter Variable: solar radiation Units: W m -2 Accuracy: ? Cost: ? Site: exposed As for net radiometers

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18 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.

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20 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.

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22 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.

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24 Sodar (Acoustic Radar) Variable: Backscatter Units: amplitude Accuracy: ? Site: away from buildings, people, & noise! Cost: ~£ ,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.

25 Sodar (Acoustic Radar) Variable: Backscatter Units: amplitude Accuracy: ? Site: away from buildings, people, & noise! Cost: ~£ ,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.

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27 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.

28 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.

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30 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

31 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

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33 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.

34 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.

35 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.

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37 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.

38 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.

39 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.

40 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.


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