Temporal Decorrelation of X-Band Backscatter from Wind-Influenced Vegetation

The temporal decorrelation characteristics of X-band Radar backscatter from wind-influenced vegetation were investigated using a short-range CW radar. Radar reflectance data were gathered on various types of individual trees from a distance of approximately 30 m. The windspeed was monitored during each measurement, which lasted 5 s. The crown cover and the mean leaf area of the trees were also recorded. Autocovariance plots were generated for each measurement, from which the decorrelation time was estimated. As expected, the return signals decorrelated faster at higher wind speeds. However, the decorrelation time was also found to depend on the tree type, tree structure, and leaf cover characteristics. Measured decorrelation times for moderate winds (7–9 m/s) were often between 40–60 ms, although the lowest decorrelation time measured under these conditions was 14 ms for the Eastern Cottonwood. In lighter winds (1–4 m/s), decorrelation times were much longer, and there was substantial spread in the data.