Observations of radar echo propagated on a sea-ice field

Intensities of the radar echo change remarkably hour by hour or day by day during the existence of sea ice off the Okhotsk Sea coast of Hokkaido. One of the causes for the change in radar echo intensity is a change of a propagative channel for radar waves, as the meteorological conditions change. In order to verify this frequency distributions of K, the effective Earth's radius factor, were obtained corresponding to the change in the maximum observable area, by analyzing the daily weather reports (rawinsonde data). It was understood that the maximum observable area depended upon the change in K. Moreover, it was found that this change depended also upon the anomalous propagation, which is a phenomenon characteristic of the sea ice field.