臺灣地區地形起伏劇烈，氣候型態多樣，且受東亞季風及颱風影響，降雨分布呈現明顯的時空不均特性。近年來，隨著全球氣候變遷加劇，極端降雨事件頻率與強度持續上升，使得豐水期內降雨集中、枯水期乾旱加劇，進一步惡化了降雨的不均勻性，對水資源管理與防災減災策略帶來重大挑戰。因此，瞭解未來氣候變遷情境下降雨不均勻性的變化趨勢，對於提升臺灣地區水資源調適與永續發展能力具有重要意義。本研究利用臺灣氣候變遷推估資訊與調適知識平台(TCCIP)基於IPCC第六次評估報告(AR6)的統計降尺度資料，分析24組全球氣候模式於不同暖化情境(SSP1–2.6、SSP2–4.5、SSP3–7.0、SSP5–8.5)與未來四個時段(2021–2040、2041–2060、2061–2080、2081–2100)下的日降雨資料，計算降雨不均勻性指數，包括年總降雨量50%所需的天數(WD50)、雨日吉尼指數(WDGI)與戴爾指數(TI)，以量化降雨集中程度與分布變異。並透過階層式分群法(hierarchical clustering)進行區域分類，探討不同地區降雨不均勻性之空間差異與變化趨勢。研究結果顯示，在最嚴重得暖化情情境與時段，SSP5–8.5遠未來時段相對於基期WD50減少13.23%、WDGI增加2.13%、TI增加8.34%，說明氣候變遷將使臺灣地區降雨不均勻性加劇，且於相關性分析結果顯示，在此情境下，三種指標間相關性最高，代表降雨不均勻性情況從多方面而言皆為惡化的趨勢。分群分析的結果表明在氣候變遷影響下，臺灣各區域降雨模式並未有明顯的變化，相對於基期的改變率東北部大於西南部。本研究成果可為臺灣地區面對氣候變遷下水資源調適與防災規劃提供重要參考。

Taiwan's steep terrain and monsoon-driven climate result in uneven spatial and temporal rainfall variations. Under intensified global climate change, the frequency and magnitude of extreme rainfall events are rising, leading to increased rainfall concentration during wet seasons and exacerbated droughts during dry seasons. This study investigates future changes in rainfall unevenness across Taiwan under four emission scenarios (SSP1–2.6, SSP2–4.5, SSP3–7.0, SSP5–8.5) and four future periods (2021–2040, 2041–2060, 2061–2080, 2081–2100), using daily precipitation data from 24 CMIP6 models statistically downscaled via the TCCIP platform. Three indexs were used to quantify rainfall unevenness: WD50 (wettest days to 50% of annual rainfall), wet-day Gini index (WDGI), and Theil index (TI). The results show that under the worst-case scenario (SSP5–8.5), WD50 decreases by 13.23%, while WDGI and TI increase by 2.13% and 8.34%, respectively, indicating worsening rainfall unevenness. Correlation analyses reveal strong interdependence among the indexs in this scenario. Hierarchical clustering shows that while regional rainfall patterns remain hearly unchanged, northeast Taiwan experiences greater shifts than the southwest. These findings underscore the urgent need for regional water resource adaptation strategies under future climate conditions.

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