為了增進西北太平洋熱帶氣旋 (TC) 的快速增強 (RI) 的預報能力，本研究使用了衛星遙測資料探討 RI 的前兆。分析包含深對流雲 (DCC)、降水、各種強度階段和增強類別之雲屬性，以及極深對流雲 (VDCC) 中的雲微物理特性。分析結果顯示在不同 TC 強度階段中，皆可利用 DCC作為RI前兆;而降水變數則可作為熱帶低氣壓 (TD) 和熱帶風暴階段的 RI 前兆。研究結果亦呈現 TC 中 DCC 溫度的徑向剖面和 TD 中的雲頂高度，可以清楚地將 RI 與其他增強類別區分開來。研究也發現快速增強的 TC 比緩慢增強的 TC ，於最大風速的半徑內具有更多的 DCC 覆蓋面積與雲冰水路徑 (IWP)比率，無論在何種增強階段。RI 初始時和 24 小時後的特徵是風暴當時的強度和強化率的假象。藉由本研究提高對熱帶氣旋快速增強的理解，我們發現: (1) 檢視並深入探討已知快速增強前兆（DCC 和降水）的適用性; (2)在特定強度階段，利用 TC 中的 DCC 溫度和 TD 中的雲頂高度，並使用 VDCC 中的平均 IWP 與其宿主 TC 的比率作為潛在快速增強的前兆因子。;Toward the advancement in predicting the rapid intensification (RI) of tropical cyclones (TCs) in the western North Pacific, precursors to RI are investigated. The TC’s deep convective cloud (DCC), precipitation, and cloud properties for various intensity stages and intensification categories, as well as the cloud microphysical properties in very deep convective clouds (VDCCs) are examined. This study determined the appropriateness of utilizing the DCC in all TC intensity stages, and the precipitation in tropical depression (TD) and tropical storm stages, as precursors to RI. The study indicated that the radial profile of DCC temperature in major TC, and cloud top height in TD can plainly delineate RI from other intensification categories. Rapidly intensifying TCs are found to have a greater VDCC to TC mean ice water path (IWP) ratio than slowly intensifying TCs, regardless of TC intensity stage. The characteristics at the onset and 24 h of RI are artifacts of the storm’s then current intensity and intensification rate. Results found in this study can be used to improve our understanding of TC RI, by (1) providing new insights on the suitability in using the previously known precursors to RI (DCC and precipitation), and (2) proposing potential precursors to RI at specific intensity stages (DCC temperature in major TC and cloud top height in TD), and using the ratio of the mean IWP in VDCC and its host TC.
