Summary
Comparisons are made of profiles of the refractive index structure parameter (C 2 n ) and two derived quantities, transverse coherence length (r 0) and isoplanatic angle (θ 0), from measurements taken with a suite of instruments including a 49.25 MHz pulsed Doppler radar with a phased array antenna, an isoplanometer, anr 0 system, a stellar scintillometer, and temperature fluctuation sensors mounted on a thermosonde. The radar, which obtained data from 2 to 22 km above ground level (AGL), was operated to provide 150 m height resolution ofC 2 n . The stellar scintillometer obtained aC 2 n profile defined at seven heights from 2.2 to 18.5 km AGL, while the thermosonde obtained and transmitted data every 20 m. The isoplanometer andr 0 system provided integratedpath (ground-to-space) values.
The method used for calibrating the radar is discussed as well as the angular dependency of radar-returned power as influenced by specular reflections. The method used for extracting opticalC 2 n from radar reflectivity by eliminating humidity effects is discussed, as is speculation as to differences in results found from the different measurement techniques.
Zusammenfassung
Vorliegende Studie präsentiert einen Profilvergleich des refraktiven Index-Struktur-Parameters (C 2 n ) und zwei abgeleiteter Größen, der transversalen Koherenzlänge (r 0) und des isoplanen Winkels (θ 0), aufgrund von Messungen mit einer Reihe von Instrumenten, u.a. mit einem gepulsteten 49.25-MHz-Doppler-Radar mit einer Phasenfeld-Antenne, einem Isoplanometer, einemr 0-System, einem Stellar-Scintillometer und Temperaturschwankungs-Sensoren auf einer Thermosonde. Der Radar, mit dem Datenmaterial in einer Bandbreite von 2 bis 22 km über Grund gesammelt werden konnte, war auf Datenmessungen vonC 2 n in einer Auflösung von 150 m eingestellt.
Das Stellar-Scintillometer erbrachte einC 2 n -Profil definiert für 7 Höhenstufen im Bereich von 2.2 bis 18.5 km über Grund während die Thermosonde Werte in 20 m-Stufen ermittelte. Das Isoplanometer und dasr 0-System erbrachten Integral-werte bis zu einer bestimmten Höhe über Grund.
Sowohl das Eichungsverfahren des Radar, als auch die Winkelabhängigkeit der Stärke des reflektierten Signals von spiegelnder Reflexion werden im folgenden besprochen, als auch die Methode zur Filterung von optischen Reflexionen imC 2 n aus den Radarreflexen durch Ausschaltung von Feuchtigkeitseinwirkungen. Zuletzt werden die Unterschiede in den Resultaten verschiedener Messungsmethoden zu klären versucht.
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Eaton, F.D., Peterson, W.A., Hines, J.R. et al. Comparisons of VHF radar, optical, and temperature fluctuation measurements ofC 2 n ,r 0 andθ 0 . Theor Appl Climatol 39, 17–29 (1988). https://doi.org/10.1007/BF00867654
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DOI: https://doi.org/10.1007/BF00867654