Turbulence: A Significant Role in Clear-Air Echoes of CINRAD/SA at Night

It is commonly believed that clear-air echoes detected by weather radars are caused by atmobios migration. However, clear-air echoes are sometimes inconsistently related to the activity of living creatures. In some cases, the characteristics of radar products seem to conform to biological scattering...

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Bibliographic Details
Published in:Remote sensing (Basel, Switzerland) Switzerland), 2023-04, Vol.15 (7), p.1781
Main Authors: Teng, Yupeng, Li, Tianyan, Ma, Shuqing, Chen, Hongbin
Format: Article
Language:English
Subjects:
aeroecology
Birds
clear-air echo
Diurnal variations
Echoes
Energy dissipation
Environmental protection
Frequency distribution
Laboratories
Meteorological radar
Meteorological stations, Radar
Night
Radar
Radar systems
Remote sensing
Reynolds number
Superhigh frequencies
troposcatter propagation
Turbulence
Turbulent mixing
Velocity
Wavelength
Weather
Weather forecasting
weather radar
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Summary:It is commonly believed that clear-air echoes detected by weather radars are caused by atmobios migration. However, clear-air echoes are sometimes inconsistently related to the activity of living creatures. In some cases, the characteristics of radar products seem to conform to biological scattering, but the movement of echoes cannot be observed. For these reasons, we sought to expand the cause of clear-air echoes from a Chinese Doppler S-band Weather Radar (CINRAD/SA) in Beijing. Some contradictions were discovered in a case which diverged from previous conclusions. It was found that the progression and movement of clear-air echoes do not conform to the rules of biological activities. The frequency distribution of dual-wavelength ratio peaks is 21.5 dB, which is in accordance with Villars–Weisskopf’s turbulence theory. From 1 May to 20 May, the 58% dual-wavelength ratio between the S-band and the X-band was distributed between 18 dB and 24 dB. These results show that more than half of the clear-air echoes of CINRAD/SA at night were caused by turbulence in Beijing. A new model of troposcatter propagation, the reflecting-layers model, was then introduced to explain the radar observations. According to the reflecting-layers model, the echoes’ diurnal variation and reflectivity characteristics are attributed to the effects of turbulent mixing. Excessive turbulent mixing affects the generation of the reflective layer, thereby weakening the echo signal. It is necessary to re-examine the position of turbulence in clear-air echoes.
ISSN:2072-4292
2072-4292
DOI:10.3390/rs15071781