快速增強與緩慢增強颱風的雲微物理特徵與降雨類型之比較研究
Authors: 黃詣軒 黃詣軒 , 楊明仁 楊明仁 
Published: April 2024

<p>為了討論快速增強(Rapid Intensification; RI)和緩慢增強(Slow Intensification; SI)颱風之間的降雨類型和雲微物理特徵的差異此，我們分析SSMIS (Special Sensor Microwave Imager/Sounder)衛星酬載儀器反演的冰水路徑(Ice Water Path; IWP)、雨水路徑(Rain Water Path; RWP)及紅外頻道的亮度溫度(Brightness Temperature)，並進行WRF (Weather Research and Forecasting)模式的數值模擬，以討論RI和SI颱風間的降雨類型和雲微物理特徵之差異與其演變比較。</p>
<p>從SSMIS觀測資料中，我們發現在2倍最大風速半徑（RMW）範圍內，RI颱風的IWP與RWP量值在增強開始前12小時後會大於SI颱風的對應量值。且在增強開始前12小時和增強開始後的12及24小時，IWP和RWP量值在2倍RMW範圍內，RI颱風的IWP/RWP量值顯著多於SI颱風的量值，而且此差異達到95%信心水準。紅外頻道的亮溫資料指出，在增強前12小時，颱風3倍RMW內的區域之RI颱風個案的亮溫低於SI颱風個案，並於增強開始後2倍RMW內，多數區域RI颱風紅外的亮溫顯著低於SI颱風的量值(達到95%信心水準)，尤其是在上風切處格外顯著。</p>
<p>在SSMIS衛星觀測與WRF模擬結果中，我們發現於颱風增強開始前，IWP和RWP在下風切處的量值大於上風切處的量值，其中又以Downshear Left (DL)象限的量值最大。在RI開始後，Upshear Left (UL)象限中的IWP和RWP逐漸增大，但是SI的颱風並沒有出現類似的演變。同時我們發現，RI颱風個案在其RI正要開始前，IWP與RWP及對流有發生快速減弱的情形。在WRF控制組模擬RI和SI颱風個案的降水類型差異比較中，我們發現在進行分析的大多數時段中，RI 颱風個案中DL和UL象限的深對流（Deep Convection; DC）和中等對流（Moderate Convection; MC）的比率大於SI 颱風個案的比率。此外，不論RI或SI的颱風個案其上風切處的層狀降水(Stratiform; ST)面積，均在增強(RI或SI)開始的前後時間有逐漸增加的情形。</p>
<p>&nbsp;</p><p>The differences and evolution of rainfall regimes and microphysics characteristics between rapid-intensification (RI) and slow-intensification (SI) tropical cyclones (TCs) are examined in this study. We have analyzed the ice water path (IWP) and rain water path (RWP) retrieved from the Special Sensor Microwave Imager/Sounder (SSMIS), brightness temperaute from infrared channel, and conducted the Weather Research and Forecasting model (WRF) simulations to investigate the differences and evolution of rainfall regimes and microphysics characteristics between RI and SI TCs.</p>
<p>From the SSMIS observations, we found that the IWP and RWP in RI TCs were greater than those in SI TCs within twice the radius of maximum wind speed (RMW) 12 hours before the RI onset. The differences in IWP and RWP between RI and SI TCs within the RMW were significant at the 95% confidence level at the RI/SI onset and within twice the RMW at 12 hours before, 12 hours after, and 24 hours after the onset. The brightness temperature from infrared channel indicated that, at 12 hours before onset, the brightness temperature of the RI cases was lower than that of the SI cases within 3 times of RMW. After the onset, the RI cases exhibited significantly lower infrared brightness temperatures compared to the SI cases at the 95% confidence level within most areas within twice RMW. This difference was particularly evident in the upshear quadrant.</p>
<p>Both the SSMIS observations and WRF simulations showed that the IWP and RWP were generally larger in the downshear flank before the onset, especially in the downshear left (DL) quadrant. The IWP and RWP in upshear left (UL) quadrant gradually became larger after the RI onset, yet similar evolution did not occur in SI TCs. The IWP and RWP were quickly weakened just before the RI onset in RI TCs.</p>
<p>We also compared the precipitation regime differences between the RI and SI TCs. We found that the ratios of deep convection (DC) and moderate convection (MC) at the DL and UL quadrants in RI TCs were greater than those in SI TCs for most periods we analyzed. The ratios of stratiform precipitation (ST) at the UL and upshear right (UR) quadrants gradually increased after the RI/SI onset.</p>
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