The National Institute of Information and Communications Technology in Japan has developed vehicle earth stations equipped with an antenna system for the automatic tracking of the Wideband InterNetworking engineering test and Demonstration Satellite “KIZUNA”(WINDS), making it possible to form a satellite link while moving. However, shadowing can have a large impact on satellite communications using directional Ka-band antennas with high rectilinearity. It is estimated that the degree of shadowing due to trees varies with seasons, which is a function of seasonal leaf cover. Therefore, we measured the potential seasonal difference by comparing the attenuation of the received signal from the satellite during a year-long experiment with shadowing from several kinds of trees. No attenuation fluctuations were observed from evergreen trees, whereas seasonal attenuation fluctuations were confirmed from deciduous trees.