Page 28 - ITU Journal: Volume 2, No. 1 - Special issue - Propagation modelling for advanced future radio systems - Challenges for a congested radio spectrum

ITU Journal: ICT Discoveries, Vol. 2(1), December 2019

Often, higher scintillation periods, however not as
intense as those of the afternoon, also occur close to
midnight, usually after, as can be observed in Fig. 5.
The lowest scintillation periods occur from 5 am to
9 am and 10 pm to 11 pm. Some turbulent
processes must be occurring in the atmosphere
between the more quite end of the day and the early
morning. The day variations are very similar at both
frequencies as can be easily observed.

Fig. 6 – Monthly cumulative distributions of the fades for the
Q-band (one year: June 2017 to May 2018)

Fig. 5 – Hourly average values of the scintillation standard
deviation at the Q and Ka band: September 2017

Lowest scintillation periods occur during the
coldest months with clear sky, foggy weather, very
dry periods (even windy ones) and, in addition, with
very weak and long lasting rain, mainly drizzle. The
worst and most sustained scintillation periods Fig. 7 – Monthly cumulative distributions of the enhancements
occur during uniform cloud cover and hot weather, for the Q-band (one year: June 2017 to May 2018)
not necessarily leading to rain. Burst scintillation As discussed in [4] for the same probability the
periods are observed during showery weather with fades are, in general, deeper than the enhancements.
dense and sparse clouds; often a rain shower is However, in spite of being true along an average
preceded by an increased scintillation period that is year, the difference is very small and it is not
probably due to turbulence in developing rain cells, verified for all the months.
caused by air masses down/updrafts and shear
winds. There is a significant variability of the cumulative
distributions from month to month but there is no
4.3 Distribution of fades and enhancements clear distinction between late spring, summer and

The monthly distribution of the scintillation early fall from the other periods. Higher
amplitude enhancements,  (dB), and fade depth, temperatures but clear sky and higher pressures
+
 , for a full year are depicted, respectively, in Fig. 6 are balanced by lower temperature but often
−
and Fig. 7 for the Q-band. cloudier conditions during the other periods.

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