Flux Tower

Gas Analyser

The LI-7500DS uses non-dispersive infrared spectroscopy to measure CO₂ and water vapor densities in air. Infrared radiation is transmitted through temperature-controlled optical filters, then through the open sample-path to a thermally regulated lead selenide detector. Some of the infrared radiation is absorbed by CO₂ and water vapor in the sample path. Gas densities are computed from the ratio of absorbed radiation to a reference.

Sonic Anemometer

The pulse-type sonic anemometer transmits sonic energy in bursts over the path of interest. Sonic pulses are transmitted in opposite directions over the same path on each axis of measurement. Pulses travelling with the wind arrive sooner than those travelling against the wind.

Sonic temperature measurements exploit the dependence of the speed of sound on the density, and hence temperature, of the air through which the sound travels.

Fluxes

Combining high rate measurement from the sonic and the gas analyser and using eddy covariance techniques a rage of flux measurements can be made.

The gas analyser and sonic are serviced before deployment or every two years: whichever is the sooner.

Both units can be serviced and re-calibrated in the field id required. The manuals supplied with the system provide details on how to do this.

Costs

• Instrument Insurance
  • This system must be insured by the user for £50K and covers loss, theft or damage to the instrument: damage is that over and above general wear and tear. The system has been designed to be rugged and autonomous. Even so, the end-user must respect the fact that the system is a precision optical instrument that must be treated with great care.
  • The user is responsible for the instrument from the time it leaves the AMOF to the time it is returned and signed off as in an acceptable operating condition by the IS: this will be done as soon as is possible on its return.
• Public Liability Insurance
  • The AMOF is not liable for any damage or injury arising from the deployment or operation of this instrument when unattended by the IS.
• Shipping Expenses
  • The user is liable for all costs arising from the shipping of the instrument both to and from a deployment.
• IS T&S
  • The user is responsible for coving the travel and subsistence expenses of the IS while attending the instrument.

Shipping

The system when packed ready for shipping consists of six boxes of various size and weight

Please contact the facility for more details

For the best results, the site should be open in all directions with no obstacles that will impact the flow no closer than 50m.

The stem requires mains electricity. The system will accept either 240 or 110 VAC but it is recommended on safety grounds that 110 VAC is supplied.

The logging system is self-contained but itis recommended that if possible the logger be connected to a network as this will allow remote access, monitoring, and control.

Manual handling

• A procedure appropriate to lifting a heavy object should be used when lifting any of the boxes. This procedure consists of bending at the knees while keeping your back straight and upright.
• Cables kept away from pathways; held overhead height if necessary.
• Guys and ground anchors should be made visible and clearly marked
• Mast must be assembled and installed by trained personnel only – a minimum of 4 people required.
• When erecting the mast safety boots and hard hats are recommended.
• No attempt should be made to erect the mast in wind conditions over 10ms-1
• MAst rigging should be checked weekly

Electric safety

• Check all module casings and cables are in good condition before switching on.
• Attach all cables before switching on at the mains. All equipment electrical safety tested.

Attended operation

• There is no requirement for the system to be attended during operation from a safety standpoint.

COSHH

• Ascarite II
• Magnesium Perchlorate

Mast

• 10m height
• 10m radius circular footprint
• 3 x 10ft Triangular lattice mast sections
• hinged base
• 6 guys at 5m
• 6 guys at 9.5 m
• 12 ground anchors (6 and 6 spare)

Power

• 24Vdc power supply provided
• This takes 240V or 110VAC
• 5 m DC power cable to system interface
• 110V 16 A Cform connector on supply
• 110V (16 A) (yellow) to 240V (16A)(blue) pigtail

System interface

• Contains logger
• Contains USB storage disk
• Connections to Sonic, Gas analyser, and GPS
• Network Connection

Field Data

• The instrument produces a range of out files and all are text format.
• The user can download (but not delete) this data from the instrument but it should be noted that this data will not have been quality controlled.

Archive Data

• Data is provided in NetCDF files following the AMOF data standard
• Files contain no more than 24hr of data.
• Instrument name is
  • ncas-flux-1
  • ncas-flux-2
  • ncas-licor-1
  • ncas-licor-2
  • ncas-sonic-1
  • ncas-sonic-2
• The data product(s) associated with this instrument:
  • flux-components
  • flux estimates
  • mean-co2-h2o
  • mean-winds
• Example data file
  • How to use example data
  • ncas-flux-1_ral_29001225_flux-components_v0.1.nc
  • ncas-flux-2_ral_29001225_flux-components_v0.1.nc
  • ncas-flux-1_ral_29001225_flux-estimates_v0.1.nc
  • ncas-flux-2_ral_29001225_flux-estimates_v0.1.nc
  • ncas-licor-1_ral_29001225_mean-co2-h2o_v0.1.nc
  • ncas-licor-2_ral_29001225_mean-co2-h2o_v0.1.nc
  • ncas-sonic-1_ral_29001225_mean-winds_v0.1.nc
  • ncas-sonic-2_ral_29001225_mean-winds_v0.1.nc