Multitemporal Fluctuations in L-Band Backscatter From a Japanese Forest

摘要

The temporal variations (diurnal and annual) in arboreal and bare soil dielectric constants and their correlation with precipitation were examined for several trees in Japan. A significant (1 (standard deviation) and 2 ) increase is observed after rainfall at 89.8% and 90.5% probability. However, rainfall does not always induce significant increases. Rainfall of more than 5 mm/day can induce 1 Tree increase at a 59.6% probability. In order to examine whether the increase in affects the L-band variation in a forest, the four-year temporal variation of the L-band backscattering coefficient was estimated from observations by the Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture Radar. Observed maximum absolute deviations from the mean over the forest area were 1.0 and 1.2 dB for and , respectively, and 4.0 and 3.0 dB over open land. and rainfall correlations show that and are proportional to precipitation integrated over seven or eight days; and are proportional to precipitation integrated over three days. This finding indicates that variations influence . A stronger correlation between and precipitation is observed in several sites with low , where less biomass is expected, and several sites with high , where more biomass is expected. A weaker correlation between and precipitation is observed for several sites with high . These differences may be explained by the different contributions of double bounce scattering and potential transpiration, which is a measure of the ability of the atmosphere to remove water from the surface th