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Instrument Support Level 2

Instrument Support Level

Instrument Support Level 2

Manufacturer & Model

Degreane Horizon

CEDA Archive Name

ncas-radar-wind-profiler-1

Data Products

snr-winds

Insurance Value

£200,000

Physical Dimensions

604 cm x 220 cm x 220 cm. 1,000kg

Shipping

604 cm x 220 cm x 220 cm. 1,000kg

Daily Facility Charge

£70: when operating away from Capel Dewi. or Cardington. £50: when operating at Capel Dewi or Cardington

Calendar

Radar Wind Profiler

The Radar Wind Profiler is a ‘clear air’ pulsed UHF Doppler radar. It is used to remotely sense the wind speed and direction in the lower troposphere 24 hours a day, under all weather conditions. Wind profiles from the boundary layer wind profiler are sent to the Met Office operational team every 15 minutes, where they are used to aid the weather forecast. The wind profiler has been operated fairly continuously since August 2002 and all the data has been archived at the Centre for Environmental Data Analysis (CEDA). It is generally stationed at one of two main sites MRU Cardington, near Bedford or at the MST radar site, near Aberystwyth. The wind profiler is mounted onto a trailer so it is easy to deploy to different locations and has been involved in numerous field campaigns around Europe.

The radar consists of three panels to emit and receive three separate beams, each panel being an array of 64 collinear dipole antennas. The vertical beam from the central panel measures the vertical component of the wind. The two lateral panels situated at 90o to the back and side of the central panel provide the two oblique beams, enabling full wind vectors to be calculated.

The backscattered UHF radiation comes from two sources in the atmosphere. It is most sensitive to Rayleigh scattering from hygrometers but in the absence of precipitation, Bragg scattering occurs from refractive index gradients in the clear air on a scale of ½ a radar wavelength. The refractive index variations are caused by changes in humidity, temperature, and pressure but in the troposphere, the main cause is humidity fluctuations.

In addition to the wind speed and direction which are extremely useful for weather forecasting models, the wind profiler provides other information to the user. For example, the signal to noise ratio (SNR) profiles provides valuable insight into the structure of the atmosphere such as the height of the convective boundary layer and residual layers. The spectral width of the clear air signal is also of interest as it provides an indication of the turbulence.

This instrument has a wide range of applications including measuring and studying wind speed, wind direction, vertical velocity, boundary layer structures, residual layers, thermals, turbulence, the morning and evening transition, the entrainment zone, weather fronts, sting jets, and lower-level jets.

Transmitter frequency: 1290 MHz
Transmitter bandwidth: 10 MHz
Beam width: 8.5°
Peak power: 3500 W
Aperture: 4m2
Antenna gain: 25 dBi
Average power (low mode): 40 W
Average power (high mode): 100 W
Minimum height (low mode): 73 m (depends on pulse length)
Maximum height (high mode): 8 km (depends on atmospheric conditions)
Altitude resolution: 75 m (low mode) to 375 m (high mode)
Intrinsic wind speed accuracy: < 1m/s
Intrinsic wind direction accuracy: < 5°
Periodicity of profile computation: 15 minutes standard
Operational temperature: -20 °C to 40 °C
Operational relative humidity: 5% to 95 % without condensation
Resistance to wind: 20 m/s (average) 45 m/s (gusts)

Radars (Radio Detection And Ranging) as well as detecting fast jets and speeding cars can be used as remote sensors of the atmosphere.

The boundary layer wind profiler is a UHF Doppler radar that emits pulses of electromagnetic radiation at a frequency of 1290 MHz into the atmosphere and then listens to backscattered energy from the clear air.

By measuring the time delay between transmission and reception of the backscattered pulse, the range at which the target is positioned can be calculated.

The range equals the time delay multiplied by the speed of light and divided by 2 because the electromagnetic radiation travels to the target and then back to the receiver.

Scattering

The electromagnetic waves emitted by the boundary layer wind profiler are reflected by a number of objects including aircraft and birds but it is the weaker echoes that result from atmospheric sources, that are of interest.

At UHF frequencies electromagnetic radiation is most sensitive to Rayleigh scattering from hygrometers (water particles) but in the absence of precipitation, Bragg scattering occurs from refractive index gradients in the clear air on a scale of ½ a radar wavelength (23 cm).

Refractive index variations are caused by variations in humidity temperature and pressure but in the lower atmosphere, the main cause is humidity fluctuations.

Doppler Principle

The Doppler effect is the change of wavelength caused by the motion of the target in relation to the observer. UHF boundary layer wind profilers make use of the Doppler principle to measure the radial velocity along a radar beam which is used to calculate the wind speed and direction.

Targets moving towards the radar bunch the waves together and result in a higher frequency (shorter wavelength) being received by the radar. Targets moving away from the radar on the other hand result in a lower frequency (longer wavelength).

The frequency shift of the backscattered energy is related to the velocity at which the reflector is moving along the radar beam by this equation.

fd = 2νd / λ

f=Doppler frequency shift

νr= radial velocity (component of velocity along the beam).

Essentially, the radar provides a picture of the movement of a volume of air (the target). By measuring the radial velocity in three directions the three components of wind can be calculated using trigonometry. Note that the Doppler frequencies of atmospheric targets are very small (maximum of kilohertz) with respect to the transmitted frequencies.

The radar wind profiler requires an “OfW 225” – non-operational licence from Ofcom formally known as an “RA 322” licence. The licence has to be applied for and usually takes about 8 weeks to be granted and currently costs £50. Other countries will probably require a similar kind of licence.

The radar wind profiler is tested by the manufactures Degreane Horizon at least once a year under the maintenance contract.

The 15 minute data from the low mode is sent in near real time to the Met Office, where it is sent into the EUMETNET observation program. The quality of the wind speed and direction are monitored on a daily basis by the E-Profile network (formally known as the E-WINPROF network). The E-PROFILE Network Manager based at MeteoSwiss sends week daily reports on the radar wind profiler data and if there is any missing or suspicious data.

Consumables

The user will be expected to supply electricity, internet access, construction of a clutter fence if desired, and a sufficiently long Ethernet cable.

Costs
  • Instrument Insurance
    • This system must be insured by the user for £200K 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 instrument that must be treated with great care.
    • As part of our service the instrument will be towed to the site and setup by the instrument scientist. The instrument will be insured by the National Centre for Atmospheric Science during transportation but the user is responsible for providing insurance while it is on-site.
  • Public Liability Insurance
    • We are not liable for any damage or injury arising from the deployment or operation of this instrument when unattended by the instrument scientist.
  • 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 Radar Wind Profiler folds up onto a compact trailer that can be towed behind a suitable vehicle such as a Land Rover as shown in the photo below.

If you are shipping the instrument, it could be packed in a 40ft container and there would be lots of space for other equipment in the same container.

  • Shipping dimensions:
    • 604 cm (L) x 220 cm (D) x 220 cm (H)
  • Shipping weight:
    • 1,000 kg

The Radar Wind Profiler requires a relatively flat and firm piece of ground within 10m from a power supply either mains or generator. The wind profiler has jacks on 4 corners so it can be levelled front to back and side to side up to 0.3m. An internet connection is preferable but not essential. It is useful as it enables remote monitoring of the instrument and automated backing up the data can be set up.

The site requires an electricity supply. Internet access is normally required so that the instrument can be monitored remotely and data can be backed up to an external server.

An indoor space is required for the processing computer. It is possible that this could be one of our mobile laboratories if office space is not available.

The Degreane software is fairly robust at detecting the clear air signal from the ground clutter using sophisticated multi-peak identification. Although the instrument performs well without a clutter screen, the data quality is improved by operating the wind profiler within a clutter screen. A clutter screen is basically a fence type structure surrounding the radar wind profiler made out of either scaffolding poles or wood and covered with a ¼ inch steel welded mesh.

Manual handling
  • When moving the radar use the towing vehicle when possible and when not possible ensure that sufficient people are able to help.
  • When packing or unpacking the radar there is a danger or trapping fingers, hands or feet in some of the folding elements. Make new operators aware of the hazards.
  • Some of the metal on the radar has sharp edges so wearing protective gloves is advised. When unhitching the wind profiler from the tow vehicle ensure that the hand brake on the trailer is engaged.
Electric safety
  • Power cables on the grass should be raised to prevent grass cutters cutting through the wires.
Non-Ionising Radiation
  • Exposure to 1290 MHz non-ionising radiations (too weak to break atomic bonds).
  • There is no proven adverse health risk at this wavelength. The beams are static and vertical pointing so prolonged exposure to personnel does not occur.
Attended operation
  • Lone working is sometimes necessary field sites. When working alone inform others of where you will be and keep a mobile phone with you.
Towing
  • When towing the wind profiler there is a danger of snaking hence only people having towing experience or persons having completed a towing course should tow the trailer. Extra care should be taken when driving downhill as this is when snaking is most likely to occur.
  • Make sure the tyre pressures are correct before starting a long journey if the trailer has not been used for more than 6 months.
  • The towing speed should be appropriate for the driving conditions and it is advised not to normally exceed 55 mph.

Frequency: 1290 Mhz
Foot print:
Operational dimension: 765cm (L) x 420cm (W) (without clutter screen)
Operational dimension: 768cm (L) x 600cm (W) (with clutter screen)
Weight: 1000 kg
Power: Averages about 3000 watts for the wind profiler (maximum 3840 watts) at 230V (+/- 15%). The radar wind profiler system can be comfortably be run off two 13 amp sockets. There is a small heater and air conditioner in the box with the electronics so power consumption very dependent on how hot or cold it is.
Operation temperature: min -20°C to 30°C (but fine above 30°C in practice)
Operation relative humidity: 5% to 95% without condensation
Resistance to wind: 100km/h (average), 150km/h (gusts)

Field Data
  • The wind profiler is generally operated in a high altitude (lower vertical resolution) and a low altitude mode (higher vertical resolution).
  • The high mode can provide data from 369 m up to 8 km if the weather conditions are favourable but its vertical resolution is coarser (187 m in this case). The low mode provides data from 73 m to approximately 3.5 km at a vertical resolution of at best 75 m.
  • The wind profiler provides wind speed (m/s), meteorological wind direction (deg), vertical velocity (m/s), u is the ZONAL VELOCITY (m/s), v is the MERIDIONAL VELOCITY (m/s), signal to noise ratio (dB) of Beams 1, 2 and 3, spectral width of beams 1, 2 and 3 (m) and the skew of beams 1, 2 and 3 (m).
  • Signal-to-noise ratio

Radar wind profiler snr

  • Spectral width

radar wind profiler spectral width

  • U component

Radar wind profiler u component

  • V component

radar wind profiler v component

  • W component

radar wind profiler w component

Archive data
  • Data is provided in NetCDF files following the AMOF data standard
  • Files contain no more than 24 hours worth of data.
  • Instrument name is
    • ncas-radar-wind-profiler-1
  • The data product(s) associated with this instrument