| Summary: | We investigate the applicability of the entropy (<italic>H</italic>)/ alpha <inline-formula><tex-math notation="LaTeX">$(\bar{\alpha })$</tex-math></inline-formula> target decomposition realized by the temporally averaged coherency matrix, called temporal <inline-formula><tex-math notation="LaTeX">$H/(\bar{\alpha })$</tex-math></inline-formula>. We apply the temporal <inline-formula><tex-math notation="LaTeX">$H/\bar{\alpha }$</tex-math></inline-formula> 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 <inline-formula><tex-math notation="LaTeX">$H/\bar{\alpha }$</tex-math></inline-formula> technique to landslide monitoring to detect and investigate the temporal scattering mechanism. The study acquired long-term GB-SAR polarimetric data over the postlandslide slope, Minami-Aso, Kumamoto, Japan. The study first investigated the property of the temporal <inline-formula><tex-math notation="LaTeX">$H/\bar{\alpha }$</tex-math></inline-formula> parameters over selected land cover types by comparing it with that derived by spatial averaging (spatial <inline-formula><tex-math notation="LaTeX">$H/\bar{\alpha }$</tex-math></inline-formula>) to explain the landslide monitoring results. Also, the rainfall effects on the temporal <italic>H</italic>/<inline-formula><tex-math notation="LaTeX">$\bar{\alpha }$</tex-math></inline-formula> parameters are demonstrated. The temporal <italic>H</italic> and <inline-formula><tex-math notation="LaTeX">$\bar{\alpha }$</tex-math></inline-formula> values increase up to 0.07<inline-formula><tex-math notation="LaTeX">$^\circ $</tex-math></inline-formula> and 13.54<inline-formula><tex-math notation="LaTeX">$^\circ $</tex-math></inline-formula>, respectively, when the rainfall rate is 52.5 mm/h. The time-series analysis of the temporal <inline-formula><tex-math notation="LaTeX">$H/\bar{\alpha }$</tex-math></inline-formula> indicates an obvious temporal transition of the scattering mechanism and a change of the backscattering stationarity when a landslide occurs. The applicability of the temporal <inline-formula><tex-math notation="LaTeX">$H/\bar{\alpha }$</tex-math></inline-formula> for the change-detection is discussed by comparing it with the classical spatial <inline-formula><tex-math notation="LaTeX">$H/\bar{\alpha }$</tex-math></inline-formula> parameters.
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