冬季期間，台灣經常發生夜間空氣污染事件；然而，過去對於其物理過程的探討，往往與大氣邊界層的動力機制分開論述。本研究整合分析了夜間輻射冷卻、地表能量平衡以及夜間穩定邊界層的演變，同時也探討了污染物在垂直方向的分佈情況。我們結合了多年 (2020-2025) 在斗六地區的無人機觀測數據、三年來在中央大學32 m氣象塔的觀測資料，並透過詳細的地表能量平衡個案分析，來描述夜間穩定邊界層的結構與生命週期。 在斗六的夜間無人機觀測剖面中，約有 41% 的案例觀測到夜間逆溫現象。逆溫層底部高度的分佈顯示，夜間地表逆溫佔主導地位，約占所有案例的 56%，凸顯了地表輻射冷卻在逆溫形成中的關鍵作用，此類逆溫的強度通常為 1-3 °C/100 m。在這些穩定條件下，風速減弱且垂直混合受到抑制，導致 PM2.5 主要滯留在最低的200-300m。與非逆溫條件下的夜晚相比，逆溫夜晚的地表 PM2.5 濃度平均高出約 15%，且在強烈輻射冷卻期間，會觀測到顯著的垂直濃度梯度（從 56.4 µg m-3 到 64.9 µg m-3）。 在中央大學，氣象塔觀測數據顯示夜間穩定度頻繁發生，冬季夜間最低的20米內溫度梯度（ΔT24-4）可達 0.7-0.9 °C。個案研究分析揭示，淨輻射在日落後迅速從正值 (+60 W m-2）下降至持續的負值（-30 到 -35 W m-2），驅動地表冷卻和逆溫形成。相比之下，在清晨過渡期間，儘管淨輻射恢復為正值（>50 W m-2），感熱通量在日出後仍會維持接近零的狀態達1-2小時以上，顯示渦流混合的恢復有所延遲。值得注意的，在2026年1月4日至5日的個案中，即使在中等風速條件下（約3-5 m s-1），逆溫層仍持續存在，這表明輻射冷卻的效應可能超越機械混合的影響。 總體而言，研究結果顯示台灣的夜間空氣污染受到夜間大氣邊界層發展的影響，而此發展主要由輻射冷卻與能量分配所驅動。傍晚的快速穩定、夜間在最低 200m 範圍持續存在的分層結構，以及清晨混合的延遲，共同控制了污染物的垂直侷限與擴散。透過整合垂直量測數據、氣象塔觀測以及地表能量平衡分析，本研究為深入了解亞熱帶環境下的夜間污染過程提供了進一步的見解。;Nighttime pollution episodes are frequent during winter in Taiwan; however， the physical processes governing their formation are often discussed separately from the dynamics of the atmospheric boundary layer. This study examines the involvement of nocturnal radiative cooling， surface energy balance (SEB)， and the evolution of the nocturnal stable boundary layer (NSBL)， along with the vertical distribution of pollutants. A combined analysis of multi-year unmanned aerial vehicle (UAV) observational data at Douliu (2020-2025)， three years of measurements from a 32-meter tower at National Central University (NCU)， and detailed SEB case studies described the structure and life cycle of the NSBL. In Douliu， nocturnal temperature inversions were identified in approximately 41% of nighttime UAV profiles. The distribution of inversion base height shows that nocturnal surface inversions dominate， accounting for approximately 56% of all cases， highlighting the key role of surface radiative cooling in inversion formation and typically exhibited strengths of 1-3 °C per 100 m increase in height. Under these stable conditions， wind speeds weakened and vertical mixing was prevented， confining PM2.5 largely within the lowest 200-300 m. Surface PM2.5 concentrations were on average about 15% higher during inversion nights compared to non-inversion conditions， with pronounced vertical concentration gradients (from 56.4 µg m-3 to 64.9 µg m-3) during periods of strong radiative cooling. At NCU， tower observations show frequent nocturnal stability， with temperature gradients (ΔT24-4) reaching 0.7-0.9 °C within the lowest 20 m during winter nights. Case study analysis reveals that net radiation decreases rapidly after sunset from positive values (approximately +60 W m-2) to sustained negative values (-30 to -35 W m-2)， driving surface cooling and inversion formation. In contrast， during the morning transition， net radiation recovers to positive values (larger than 50 W m-2)， yet sensible heat flux remains near zero for more than 1-2 hours after sunrise， indicating delayed turbulence recovery. Notably， inversion layers persist even under moderate wind conditions (around 3-5 m s-1) for the case of 04-05 January 2026， suggesting that radiative cooling can dominate over mechanical mixing. Overall， the results indicate that nighttime air pollution in Taiwan is influenced by the development of the nocturnal atmospheric boundary layer， driven by radiative cooling and energy distribution. Rapid evening stabilization， prolonged nocturnal stratification within the lowest 200 m range， and delayed morning mixing together control the vertical confinement and dispersion of pollutants. By integrating vertical measurement data， observations from monitoring towers， and SEB analysis， this study provides further insights into nighttime pollution processes in subtropical environments.
