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.

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.