Portal de Periódicos da CAPES

Correlation between the aerological atmospheric refractivity and the received level of non-line-of-sight FM radio waves

2010; Volume: 30; Issue: 2 Linguagem: Inglês

10.1541/jae.30.83

0919-2050

Teruaki Yoshida, Koichi Shin, Masahiro Nishi,

GNSS positioning and interference

After the Hyogoken-nanbu earthquake in 1995, Kushida et al. reported that they had detected propagation anomalies of the non-line-of-sight FM radio wave of 77.1MHz broadcasted from Sendai. They hypothesized that the propagation anomalies were due to the ionospheric disturbances which might be affectted by the earthquake. Then, non-line-of-sight FM radio waves have been observed to clarify the hypothesis at many electromagnetic observatories. We also started observation of non-line-of-sight FM radio waves with a dual frequency method from 1996. Now, more than 140 tuners have been operated at our twelve observatories in Japan. Our previous observation results suggested that propagation anomalies might be affected by meteorological conditions rather than by the ionospheric disturbances. It is highly required to investigate the propagation characteristics of non-line-of-sight FM radio waves and the meteorological data near propagation paths. So we have been observing non-line-of-sight FM radio waves at Kajigamori electromagnetic observatory in order to clarify correlation between the aerological atmospheric refractivity and the propagation characteristics of FM radio waves. The observed FM radio wave frequencies were 88.0MHz from Oita and 83.2MHz from Miyazaki. The observation period was for 3 years from January 2006 to December 2008. It was found from our observational results that the received levels of non-line-of-sight FM radio waves had seasonal variations in their fluctuations. The fluctuation levels in summer season were larger than those in winter. They were strongly correlated with the aerological atmospheric refractivity.