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INSU/Météo VHF Radar locationsThe INSU/Météo ST (called Stratosphere-Troposphere radar) wind profiler radars are semi-mobile clear air Doppler radars which are generally situated at these locations :
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Location (freq.) Geographic Coordinates Date
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CLERMONT-FERRAND - latitude : 45 45 52 N = 45.764 Dec. 1990-Dec. 1995
(45 MHz) - longitude : 3 6 45 E = 3.112
- altitude : 394 m
CLERMONT-FERRAND - latitude : 45 43 00 N = 45.717 Oct. 1998 - present
(45 MHz) - longitude : 3 5 30 E = 3.085
- altitude : 660 m
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TOULOUSE - latitude : 43 34 N = 43.566 Feb. 1991 - present
(45 MHz) - longitude : 1 22 E = 1.366
- altitude : 158 m
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TOULON - latitude : 43 7 N = 43.116 From 1985
(45 MHz) - longitude : 5 55 E = 5.919 Feb. 1993 - present
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LANNEMEZAN - latitude : 43 7 59 N = 43.133 Oct. 1990-Dec. 1990
(45 MHz) - longitude : 0 22 1 E = 0.367 Feb. 1993 - present
- altitude : 600 m
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SAINT-MICHEL - latitude : 43 56 46 N = 43.946 Feb. 1993 - present
L'OBSERVATOIRE - longitude : 5 42 45 E = 5.713
(72.5 MHz)
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SAINT-SANTIN - latitude : 44 39 N = 44.650 Feb. 1988 - present
(961 MHz) - longitude : 2 12 E = 2.200
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45 MHz INSU/Météo VHF Radar Specifications
Transmitter:
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Frequency ........................... 45.0 MHz
Pulse Peak Power .................... 4.5 kW
Pulse Repetition Frequency .......... 6.4 kHz
Pulse Length ........................ 2.5, 15 or 25 (coded pulse) 10-6 s
Height Resolution ................... 375, 2250 or 375 (coded pulse) m
Duty Cycle .......................... 1.6, 9.6 or 16 (coded pulse) %
Receiver:
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Linearity ........................... 112 dB
Bandwidth ........................... 2 MHz
Antenna:
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Single Element ...................... Co-Co (Coaxial-Colinear) line
Number of Elements .................. 16 lines of 26 elements
Beamwidth ........................... 5.6 degrees
Gain ................................ 30 dB
Effective Area ...................... 3500 m2
Steerability ........................ vertical, 15 degrees North, 15 degrees East,
15 degrees South and 15 degrees West
Polarisation ........................ linear
Power Aperature Product ............. 2.52 x 106 Wm2
The antenna field of the 45 MHz INSU/Météo VHF Radar near CLERMONT-FERRAND is made of 2 perpendicular sets of 60 m Co-Co (Coaxial-Colinear) lines feeded without or with fixed delay, enabling the radar beam to be successively pointed vertically, and at 15 degrees off the vertical in the North, East, South and West directions, depending of a control sequence :
SIGNAL PROCESSING CHARACTERISTICS: ---------------------------------- Wind Measurement Technics ........... Doppler Beam Swinging Mode Number of Radial Gates .............. 1 to 48 (computer setting) Practical Measurement Range ......... 1.9 to 7-8 km (1.9 to 12-15 km for the coded mode) Number of Points for FFT ............ 256 Number of Coherent Integrations ..... 128 256 512 1024 2048 Maximum Radial Velocity (m.s-1 ) .... 83.2 41.6 20.8 10.4 5.2 Radial Velocity Resolution (m.s-1 ) . 0.65 0.33 0.16 0.08 0.04 Maximum Horiz. Velocity (m.s-1 ) .... 320. 160. 79. 39. 20. Acquisition Duration (s) ........... 5.2 10.2 20.5 41.0 81.9 (for 1 incoherent integration) Time Resolution (1 Windprofile) .... 1 to 3 min
In Clermont-Ferrand and Toulouse, a RASS (Radio-Acoustic Souding System) is coupled to the wind profiler radar. A step-frequency modulated sound wave, generated by a coninuous acoustic source and propagating upward in the troposphere, is tracked by a Doppler radar (VHF profiler in our case). In Clermont-Ferrand, a frequency shift of the received signal brings the speed of this sound wave (around 300 m/s) within the radial velocity range (see the above Table) of the measurements made by the Doppler radar. The acoustic temperature, whose value lies between that of the real temperature and that of the virtual temperature, is deduced from the value of the measured speed of this sound wave.
Clermont-Ferrand RASS CHARACTERISTICS:
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Acoustic Transmitter:
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Frequency ........................... modulated by DDS aroud 100 Hz
(Direct Digital Synthesis)
Modulation .......................... linear or random by steps
Power ............................... 100 W (electric), 10 W (acoustic)
Pulse Repetition Frequency .......... 0,05-0,2 Hz
Antenna:
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Type ................................ woofer-speaker and acoustic horn
Beamwidth ........................... around 50 degrees
Geometric Area ...................... 2.2 m2
Voldorad (Volcanic Doppler radar) UHF Radar SpecificationsA UHF radar is fonctionnally identical to a VHF radar, except that the electromagnetic wavelength is smaller (0,24 m instead of 6,66 m). Its vertical range is smaller, but its antenna is much smaller for the same beamwidth.Transmitter: ------------ Frequency ........................... 1,238 GHz Pulse Peak Power .................... 1 kW Pulse Repetition Frequency .......... 10 kHz Pulse Length ........................ 0,75 or 1 10-6 s Height Resolution ................... 112 or 150 m Receiver: --------- Linearity ........................... 100, 110 ou 120 dB Bandwidth ........................... 1 or 2 MHz Antenna: -------- Single Element ...................... Yagi (24 éléments) antenna Number of Elements .................. 4 Beamwidth ........................... 9 degrees Gain ................................ 24 dB Steerability ........................ azimuth and elevation orientable SIGNAL PROCESSING CHARACTERISTICS: ---------------------------------- Wind Measurement Technics ........... Doppler Number of Radial Gates .............. 1 to 40 Corresponding Measurement Range ..... 0.3 to 6 km Practical Measurement Range ......... 0.3 to 1.5 km Number of Points for FFT ............ 64 Number of Coherent Integrations ..... 10 to 100 Maximum Radial Velocity (m.s-1 ) ...... 60.5 to 6 Radial Velocity Resolution (m.s-1 ) ... 1.87 to 0.19
Specifications of the Sodar next to the 45 MHz INSU/Météo VHF Radar in Clermont-FerrandA Sodar is fonctionnally identical to a VHF radar, except that it emits acoustic soundwaves with a loud-speaker which also serves as microphone during the reception of the return sound signals.Transmitter: ------------ Frequency ........................... 2,0 kHz Pulse Peak Power .................... 150 W (electric) Pulse Repetition Frequency .......... 0.25 Hz Pulse Length ........................ 100 ms Height Resolution ................... 17 m Receiver: --------- Linearity ........................... 82 dB Bandwidth ........................... 100 Hz Antenna: -------- Single Element ...................... parabola (1.5 m diameter) Beamwidth ........................... 9.5 degrees Gain ................................ 23 dB Steerability ........................ vertical, 30 degrees North and 30 degrees East SIGNAL PROCESSING CHARACTERISTICS: ---------------------------------- Wind Measurement Technics ........... Doppler Beam Swinging Mode Number of Radial Gates .............. 35 Practical Measurement Range ......... 50 to 600 m Number of Points for FFT ............ 64 Maximum Radial Velocity (m.s-1 ) ...... 27.2 Radial Velocity Resolution (m.s-1 ) ... 0.65 Time Resolution (1 Windprofile) ..... 4 s
Y.Pointin@opgc.univ-bpclermont.fr
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