Multistatic radar observation of a fine-scale wind field with a coupling-compensated adaptive array technique

摘要

As part of the Coupling Processes in the Equatorial Atmosphere (CPEA-II) Campaign, multistatic radar observations of local wind field were conducted using the Equatorial Atmosphere Radar and two auxiliary receiver arrays in West Sumatra, Indonesia, in December 2005. For obtaining velocity estimates from atmospheric echoes received by the two small arrays that have a high sidelobe level due to their small effective aperture, an adaptive clutter rejection process is required. Because of the existence of electromagnetic coupling between antennas and the ground, the relative phase, in terms of an echo received by separate antennas, cannot be accurately predicted only with given positions of antennas and the target volume. The phase error leads to degradation of desired atmospheric echoes in the output of the adaptive clutter rejection process. In order to compensate for the mutual coupling effect, we proposed a method to estimate the phase error corresponding to several directions in which atmospheric echoes were observed with particularly high signal-to-noise ratio (SNR). The estimates were interpolated at every necessary directional point using linear fit, thereby resulting in a successful removal of ground clutters without a serious loss of SNR. With this method, we have obtained a partial data set of the wind field. The wind field in the lower troposphere shows small-scale fluctuations on a horizontal scale of ～500 m. We also present an attempt to interpret the fluctuation in a composite of multiple plane waves, employing a nonorthogonal decomposition method using a generalized inverse.