We investigate the applicability of the entropy (H)/ alpha () target decomposition realized by the temporally averaged coherency matrix, called temporal H/ . We apply the temporal H/ to ground-based synthetic aperture radar (GB-SAR) continuous monitoring data to characterize the scattering mechanism temporal change. As a case study, this work demonstrates the application of the temporal H/ technique to landslide monitoring to detect and investigate the temporal scattering mechanism. The study acquired long-term GB-SAR polarimetric data over the post-landslide slope, Minami-Aso, Kumamoto, Japan. The study first investigated the property of the temporal H/ parameters over selected land cover types by comparing it with that derived by spatial averaging (spatial H/ ) to explain the landslide monitoring results. Also, the rainfall effects on the temporal H/ parameters are demonstrated. The temporal H and values increase up to 0.07 and 13.54°, respectively, when the rainfall rate is 52.5 mm/h. The time-series analysis of the temporal H/ indicates an obvious temporal transition of the scattering mechanism and a change of the backscattering stationarity when a landslide occurs. The applicability of the temporal H/ for the change-detection is discussed by comparing it with the classical spatial H/ parameters.