Showing papers by "Guifu Zhang published in 2002"
TL;DR: In this paper, a unique dataset consisting of high-resolution polarimetric radar measurements and dense rain gauge and disdrometer observations collected in east-central Florida during the summer of 1998 was examined.
Abstract: A unique dataset consisting of high-resolution polarimetric radar measurements and dense rain gauge and disdrometer observations collected in east-central Florida during the summer of 1998 was examined. Comparison of the radar measurements and radar parameters computed from the disdrometer observations supported previous studies, which indicate that oscillating drops in the free atmosphere have more spherical apparent shapes in the mean than equilibrium shapes. Radar‐disdrometer comparisons improved markedly when using an empirical axis ratio relation developed from observational studies and representing more spherical drop shapes. Fixedform power-law rainfall estimators for radar reflectivity ( ZH), specific differential phase (KDP), specific differential phase‐differential reflectivity ( KDP, ZDR), and radar reflectivity‐differential reflectivity ( ZH, ZDR) were then determined using the disdrometer observations. Relations were produced for both equilibrium shapes and the empirical axis ratios. Polarimetric rainfall estimators based on more spherical shapes gave significantly improved performance. However, the improvement was largely in bias mitigation. Rainfall estimates with the ZH‐ZDR measurement pair had the highest correlation with rain gauge observations, the smallest range in bias factors from storm to storm, and the smallest root-mean-square error.
404 citations
TL;DR: A two-level drop size distribution (DSD) model is proposed, in which DSD parameters are assumed to be variable for representing the sampling effects and the dependence of statistical moments on the variation of D SD parameters are calculated and applied to radar-based rain estimation.
Abstract: The authors study the sampling effect on radar measurements of inhomogeneous media and the resultant rain estimation. A two-level drop size distribution (DSD) model is proposed, in which DSD parameters are assumed to be variable for representing the sampling effects. The dependence of statistical moments on the variation of DSD parameters are calculated and applied to radar-based rain estimation.
12 citations
24 Jun 2002
TL;DR: Presents a range interferometry technique to determine radial wind, where the wind velocity is obtained by the ratio of range cross-correlation function at positive and negative lags.
Abstract: Presents a range interferometry technique to determine radial wind. The wind velocity is obtained by the ratio of range cross-correlation function at positive and negative lags. The feasibility of the method is studied through error analysis. The standard error of the estimated radial wind is derived and its sensitivity to range resolution, sample time and turbulence is analyzed.
1 citations