Radar電波の異常伝播に就いて(日本航海学会第11回講演会)

抄録

In standard atmospheric condition, because of the refractive index of atmosphere decreases uniformly with height, radar wave will be bent into a slight downwards curve towards Earth's surface. But the refractive index is affected by the alteration of relative humidity and temperature with height and causes non-standard propagation of radar wave, i.e. sub-refraction, super-refaction etc. The effect of sub-refraction on the radar wave is usually to reduce detection ranges considerably and occurs mainly in cold areas, particularly icefield. In super-refraction condition, echoes may be received from longer ranges beyond the maximum ranges of the set, as Second trace echoes. We, navigator, however, may not make accurate prediction of propagation conditions, because of the factors and data couldn't be observed onboard the ship, but some knowledge of the meteorological condition likely to affect propagation may be of considerable help for the radar navigation.