Wind Profiler
A wind profiler is a meteorological measurement system that works mainly like a vertically aligned radar device . It can be used to determine the high-altitude wind at an altitude of 0.5 to 16 km and the temperature up to 4 km with high temporal resolution , typically every 30 minutes; thus they are more topical than probing the atmosphere with balloons . The data can be used directly for the initialization and adaptation of the weather models and is used for the most accurate weather forecast possible . Wind Profilers work fully automatically and can therefore be operated with little staff.
 
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Wind profiler in Germany |
Measuring principle
Wind speed
A pulsed electromagnetic wave is emitted into the troposphere via a phase-controlled group antenna ( phased array antenna ) ; At least three different beam directions are used to measure wind using the DBS method ( Doppler beam swinging ). The electromagnetic waves are scattered by inhomogeneities in the refractive index . The Doppler shift and thus the radial wind speed can be determined from the phase change of the backscattered wave .
temperature
The temperature is measured according to the principle of the radio-acoustic sounding system . Four large loudspeakers emit around 135 dBa sound waves into the atmosphere. The resulting pattern of density - fluctuations is scanned by the radar wave, the speed of sound as a function of the measured wavelength of a known frequency is determined. The temperature is then derived from the speed of sound using Laplace's relation . The range of the temperature measurement is limited to 4 km by the range of the acoustic signal.
Frequencies used
Any radar frequency can be used as a transmission frequency to determine wind speeds . There is a compromise to be made:
- the higher the transmission frequency, the higher the Doppler frequency at the same wind speed, which is why higher frequencies offer better measurement accuracy ; however, they are very strongly attenuated within clouds and therefore do not have a long range.
- lower frequencies can penetrate denser cloud cover , but have poorer accuracy.
Ground based
To measure from the ground, lower frequencies are generally in the HF up - UHF - band used; Frequencies around 50 MHz can even penetrate thick storm clouds . In Germany approved frequencies for (mostly down-to-earth) wind profile radar devices are:
| min. frequency | Max. frequency | in the frequency band |
|---|---|---|
| 46 MHz | 68 MHz | HF |
| 470 MHz | 790 MHz | UHF |
| 1,260 MHz | 1,300 MHz | L. |
Satellite-based
In the case of satellite- based radar devices (radiation downwards ), limitations in accuracy due to the divergence of the electromagnetic waves must be accepted due to the usually very high height of the orbit above the earth's surface or the cloud cover . This can be compensated by choosing extremely high transmission frequencies and the resulting higher directivity with smaller geometrical dimensions of the antennas; the higher attenuation of the atmosphere is in measurements from the space only effective on a very short piece of the propagation path. The following frequency bands are also used from satellites to explore weather phenomena:
| min. frequency | Max. frequency | in the frequency band |
|---|---|---|
| 5.250 GHz | 5.255 GHz | C. |
| 9.300 GHz | 9.900 GHz | X |
| 13.25 GHz | 13.75 GHz | Ku |
| 24.05 GHz | 24.25 GHz | K |
| 35.5 GHz | 36.0 GHz | Ka |
| 94.0 GHz | 94.1 GHz | W. |
| 130.0 GHz | 134.0 GHz | F. |
| 237.9 GHz | 238.0 GHz | J |
history
- 1966–1969 first attempts at wind measurements using radar in Wallops Island
- 1975: first special radar for high-altitude wind measurements goes into operation in Boulder (Colorado) (sunset radar)
- 1976: SOUSY (Sounding System) of the MPAE works near Katlenburg-Lindau
- 1984: Colorado Wind Profiler Network starts work with five profilers
- 1991: Wind Profiler Demonstration Network works with 32 systems
- from 1996: the German Weather Service starts developing and building a Profiler Network in Germany. The prototype will be put into operation at the Lindenberg Meteorological Observatory ( Brandenburg ). Systems in Ziegendorf ( Mecklenburg-Western Pomerania ), Nordholz ( Lower Saxony ) and Bayreuth ( Bavaria ) follow .