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Chilbolton Facility for Atmospheric and Radio Research (CFARR): Gas analyser and Sonic anemometer data

Update Frequency: Monthly
Latest Data Update: 2019-12-10
Status: Ongoing
Online Status: ONLINE
Publication State: Published
Publication Date: 2009-07-29
Download Stats: last 12 months
Dataset Size: 1.77K Files | 113GB


A sonic anemometer and a gas analyser measuring water vapour and carbon dioxide are co-located within a compound dedicated to measuring fluxes using the eddy covariance method at Chilbolton Observatory. The eddy covariance technique is an atmospheric measurement method used to calculate vertical turbulent fluxes within the atmospheric boundary layer. This is the lowest region of the troposphere and is usually well mixed, particularly during daylight hours, due to convective heating from the sun. It is this motion in the lower troposphere that makes the technique possible.

In order to properly measure the turbulent properties of the atmosphere the measurements must be made at a high frequency - 20 Hz for the Chilbolton Observatory system.

A sonic anemometer measures the 3 orthogonal components of the wind velocity by measuring the changes in the time of flight of sonic pulses between 3 transmitter/receiver pairs as a result of the air velocity.

A gas analyser measures the absorptance of radiation along a fixed path and uses this to determine the concentration of a gas in air. For each gas the absorptance at 2 wavelengths is measured 152 times per second, one affected by that gas and the other unaffected.

There are more accurate instruments available for measuring water vapour and carbon dioxide (e.g. a relative humidity sensor for water vapour) but the benefit of the gas analyser is that it has a sufficiently fast response to resolve the rapid changes in concentration as a result of turbulence.

Citable as:  Agnew, J. (2009): Chilbolton Facility for Atmospheric and Radio Research (CFARR): Gas analyser and Sonic anemometer data. NCAS British Atmospheric Data Centre, date of citation.
Abbreviation: Not defined
Keywords: CFARR, gas analyser, anenometer


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Use of these data is covered by the following licence: When using these data you must cite them correctly using the citation given on the CEDA Data Catalogue record.
Data lineage:

Data are collected by the Chilbolton Facility for Atmospheric and Radio Research (CFARR) before being checked by the instrument scientist and then delivered for archiving with the data centre.

Data Quality:
Data are checked by CFARR staff prior to submission to BADC
File Format:
Data are netCDF formatted

Related Documents

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Process overview

This dataset was generated by instruments deployed on platforms as listed below.
Output Description


  • var_id: licor7500_agc_code
  • long_name: Code indicating transmission of Licor 7500 window.
  • long_name: Vertical Windspeed
  • names: Vertical Windspeed
  • units: K
  • standard_name: air_temperature
  • var_id: air_temperature
  • long_name: air temperature measured by sonic anemometer
  • units: m
  • standard_name: height
  • var_id: height
  • long_name: height of ground level above mean sea level (Ordnance Survey Great Britain)
  • units: m
  • standard_name: height
  • var_id: height
  • long_name: height of instrument above ground
  • units: mol m-3
  • var_id: raw_mole_concentration_of_carbon_dioxide_in_air
  • long_name: raw mole concentration of carbon dioxide in air
  • units: mol m-3
  • var_id: raw_mole_concentration_of_water_vapor_in_air
  • long_name: raw mole concentration of water vapor in air
  • units: m s-1
  • standard_name: eastward_wind
  • var_id: eastward_wind
  • long_name: speed of the wind towards the east
  • units: m s-1
  • standard_name: northward_wind
  • var_id: northward_wind
  • long_name: speed of the wind towards the north
  • units: m s-1
  • standard_name: upward_air_velocity
  • var_id: upward_air_velocity
  • long_name: speed of the wind vertically upwards (negative is downwards)

Co-ordinate Variables

  • units: degree_north
  • standard_name: latitude
  • var_id: latitude
  • long_name: latitude
  • units: degree_east
  • standard_name: longitude
  • var_id: longitude
  • long_name: longitude
  • standard_name: time
  • var_id: time
Temporal Range
Start time:
End time:
Geographic Extent

Related parties
Authors (1)
Principal Investigators (1)