雷達數位化資料客觀分析

Objective Analysis of Digital Radar Data

蘇良石(Liang-Shur Su)

《大氣科學》 16卷4期 (1988/12) Pp. 373-389

摘要

利用雙線性內插法將雷達觀測資料自球座標轉換至直角座標網格上時，常導致一些異常的回波圖形產生。特別是當不連續之回波界面存在時此現象最為顯着。此乃由於雷達觀測資料的解析度並非均勻使然，尤其是方位角和仰角解析度會隨探測的距離增遠而變差，以致無法將降水分佈的實際情形完全顯示出來。本文以模擬之雷達回波資料，分別經採用零階及一階內插方法並選取三種不同的影響半徑進行實驗，俾便探討異常圖形產生的原因及其影響，繼而尋求消除該項缺失的可行途徑。為了便於將分析結果與回波模型比較，又將分析資料經修勻後繪成垂直剖面圖；結果顯示，欲使波長等於兩倍資料平均間距之觀測資料場，經一階內插至網格點後之最終反應函數值為e^(-1)，則最佳影響半徑應選取為資料平均間距的2.4倍。同時亦發現，資料若使用三維的內插法，要比僅在特定層中作二維內插所獲之結果為佳。

關鍵字

雷達 ； 客觀分析

並列摘要

Using typical bilinear interpolation methods in deriving Cartesian grid values from spherical radar data, artifacts are easily produced. These artefacts arise from an angular resolution in the radar measurement grid which is too low compared to the typical spatial variabilities of echoes especially in the vertical near discontinuities at horizontal echo boundaries.In order to illustrate those undesired artifacts produced by interpolation from coarse data, two types of simulated echo patterns and two basic interpolation schemes: zero order and first order interpolation have been studied.In this study, we select three values of scan radii to perform experiments. In order to make a comparison between analytic results and model echo patterns, various vertical cross sections through the same model echo fields obtained by both interpolation methods have been plotted.It is evident that the optimum radius of influence which gives maximum response of no more than 0.369 at the minimum resolvable wavelength is derived and proved to be 2.4 times of the mean data spacing.In the meanwhile, it is also found that the extension of the two dimensional interpolation scheme to three dimensions will improve the final results.

並列關鍵字

Radar ； Objective analysis