科研之友
微信
新浪微博
Facebook
分享链接
摘要
By formulating the effect of radar velocity aliasing and the resulting zigzag discontinuities into the cost function for the velocity azimuth display (VAD) analysis, the previously developed alias-robust VAD analysis, called AR-VAD, can estimate the horizontal mean wind by directly fitting the VAD uniform-wind model to raw aliased radial-velocity observations. In this article, the AR-VAD analysis is further developed into a two-step alias-robust variational analysis, called AR-Var, to estimate the radial-velocity field beyond the VAD uniform-wind model from raw aliased radial-velocity observations on each range circle. In the first step, the original AR-VAD analysis is modified to fit the raw aliased radial-velocity observations around each of the two zero radial-velocity points on the selected range circle. The two analyzed radial-velocity fields are then combined into a single radial-velocity field not rigidly constrained by the VAD uniform-wind assumption. This combined radial-velocity field represents an improved fit to the observations over the entire range circle and thus can be used as the first-guess background to refine and perform the AR-Var analysis in the second step. The two-step AR-Var analysis can provide a reliable reference radial-velocity field for the reference check in radar velocity de-aliasing even when the Nyquist velocity is reduced below 12 m s(-1), and this is illustrated by both idealized and real examples.
