engleski

A study of the modified refraction indices over the Alpine and sub-Alpine region

Non-standard, anomalous propagation conditions for radio waves in the atmosphere are frequent over the Alpine and sub-Alpine regions. These phenomena could be examined by measuring: pressure, temperature and dew point using aerological balloon probes and computing, so called, modified refraction index. This work is based on six and a half years long data series of vertical profiles of the modified refraction indices for twelve aerological stations. All three kinds of anomalous propagations: subrefractions, superrefractions and radio ducts show annual variations. The most frequent anomalous propagation phenomenon is superrefraction, followed by subrefraction and then radio-ducts. According to the vertical distributions, the radio ducts appear at the surface and at low heights in the majority of cases, superrefractions are slightly more elevated, while subrefractions are predominantly elevated phenomena. Using all data and computing skewness and kurtosis for the distributions of the vertical gradient of the modified refraction index, three classes were detected.

radiowave; refraction; atmosphere

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