利用剖風儀雷達分析台灣及帛琉地區的降水融解層特性; Analysis of Precipitation Melting layer by Wind Profilers' data at Taiwan and Palau.

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Title:	利用剖風儀雷達分析台灣及帛琉地區的降水融解層特性;Analysis of Precipitation Melting layer by Wind Profilers' data at Taiwan and Palau.
Authors:	柯人豪;Ren-hao Kel
Contributors:	太空科學研究所
Keywords:	降水;融解層;亮帶;剖風儀;雷達;melting layer;bright band;precipitation;wind profiler;radar
Date:	2011-07-21
Issue Date:	2012-01-05 14:11:07 (UTC+8)
Abstract:	我們利用台灣2006年和帛琉2003－2006年的剖風儀雷達觀測資料，運用了一套演算法，將具有溶解層訊號的層狀型（Straitiform）降水回波資料篩選出來，利用篩選出的範圍較正訊號信噪比（Signal to Noise Ratio，簡稱SNR）決定亮帶（Bright Band）高度，以及都卜勒垂直速度（Doppler Vertical Velocity，簡稱DVV）決定雨高，將它們的月平均求出並與TRMM衛星的亮帶資料和無線電探空儀觀測的0度C 等溫面高度相比較，發現台灣地區月平均資料具有顯著的月變化現象，帛琉地區則無。接著我們進一步將台灣的資料分成五大類來探討：（一）春季鋒面系統、（二）梅雨鋒面系統、（三）颱風系統、（四）午後對流系統、（五）秋季鋒面系統。帛琉的資料則依水平緯向風場變化分為東風時期（Easterly Regime）和西風時期（Westerly Regime）來探討。另外我們利用了三種方法決定溶解層的厚度值：（一）將探空儀觀測時間一小時內的0℃高度與雷達觀測的平均雨高相減。（二）將亮帶高資料減去雨高資料。（三）利用觀測到的每一筆SNR 資料斷面圖，定出他們的亮帶上下界並相減。發現第一種方法因為在帛琉觀測的探空測站和剖風儀較接近，使成效較佳，第二、三種方法在台灣及帛琉的結果都無顯著的季節變化。 We used an algorithm to pick out the data with melting layer signal produced by straitiform precipitations from the data observed by the UHF Wind Profilers at Taiwan, 2006 and Palau, 2003–2006. Then we defined the “bright band” heights by range-corrected SNR data and the “rain top” heights by Doppler vertical velocity (DVV) data and averaged them monthly, comparing to the bright band heights data by the TRMM satellite and 0 degree C isothermal heights data by radiosonde. We found the notable phenomenon of seasonal variation at Taiwan but at Palau. Then we classified these data at Taiwan into 5 categories: (1) spring frontal system, (2) Mei-Yu frontal system, (3) Typhoon and (4) afternoon shower, and (5) autumn frontal system. Using the zonal wind data we divided the data at Palau into easterly regime and westerly regime then analysed them. On the other hand we used three methods to define the thickness of melting layer: (1) Taking differences of 0degree C isotherm heights by radiosonde and rain top heights by wind profiler within one hour after each launching. (2) Taking differences of bright band heights and rain top heights both by wind profiler. (3) Taking differences between the upper bound and lower bound of each SNR profiles using an algorithm. We found the better results at Palau by first method due to the nearer distance between radiosonde and wind profiler. And the second, third method we haven’t found the notable phenomenon of monthly variation both at Taiwan and Palau.
Appears in Collections:	[Graduate Institute of Space Science] Department of Earth Sciences

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