We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
A two-step variational method for analyzing severely aliased radar velocity observations with small Nyquist velocities.
- Authors
Xu, Qin; Nai, Kang
- Abstract
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.
- Subjects
AZIMUTH; VELOCITY; WIND measurement; DOPPLER radar; NYQUIST diagram
- Publication
Quarterly Journal of the Royal Meteorological Society, 2013, Vol 139, Issue 676, p1904
- ISSN
0035-9009
- Publication type
Article
- DOI
10.1002/qj.2075