Thursday, 17 September 2015
Oklahoma F (Embassy Suites Hotel and Conference Center )
Wide interest and considerable effort have been given to estimate the specific differential phase (Kdp) and more recently the backscatter differential phase (dhv) because of their independence to radar miscalibration and attenuation. However, their typical estimations require a substantial amount of smoothing processes. This might lead to undesirable spatial resolutions, significant biased estimation, and therefore unreliable weather radar observations. In this work, an advanced method to estimate Kdp and dhv from pure rain at X-band frequencies is proposed. The method aims to obtain high spatial resolution of Kdp and dhv estimators while controlling their inherent bias-variance dilemma. The method consists of 4 processes: 1) translate theoretical relationships between polarimetric variables, 2) isolate dhv from the total differential phase, 3) scale range derivatives of the propagation differential phase component, and 4) distribute them among range gates. In addition, the variance of Kdp and dhv were mathematically formulated for quality control scheme. This method was applied to two storms events, stratiform and convective, using the horizontally scanning polarimetric X-band weather radar in the Netherlands. Results have shown that estimated Kdp and dhv were able to retain the spatial variability of storms, few tens of meters, and produce a variance similar to or less than those of conventional approaches. It is foreseen that the proposed method would improve the quality of radar-based rainfall and raindrop size distribution retrieval as recommended by both, urban-hydrology and weather-forecast users.
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