加拿大阿尔伯塔大学Luo, Kaiwei和Wang, Xianli课题组最新的研究揭示了干旱引发并维持北美地区的夜间火灾。相关论文于2024年3月13日发表在《自然》杂志上。

课题组人员研究了2017至2020年期间，北美23,557起火灾的昼夜周期，并使用地球同步卫星数据和地面火灾记录确定了1,095起夜间燃烧事件(OBEs，每个事件都被定义为火灾彻夜燃烧的夜晚)。研究证明，干旱条件促进了火灾的夜间燃烧，这是助长形成大型活动火灾的关键机制。共由99%的出OBEs与大型火灾(＞1000ha)有关，其中20%的大火中至少发现一次OBE。OBE在着火后早期发生，其频率与火势大小呈正相关关系。

尽管气候变暖正在削弱夜间火灾的气候屏障，但研究发现，近期大型火灾中OBEs的主要驱动因素是累积的燃料干燥度和可用性(即干旱条件)，这往往会导致一场野火连续数天甚至数周发生OBEs。至关重要的是，研究人员表明，白天干旱指标可以预测是否会在第二天晚上发生OBE，这可能有促进夜间火灾的早期发现和管理。该课题组人员还观察到近几十年来，有利于OBEs的火灾天气条件增加，表明昼夜火灾周期的加速中断。

据悉，北美地区出现的夜间火灾的驱动因素和影响此前未知。这一值得注意的现象挑战了人们对“白天活跃，夜晚安静”的昼夜火灾周期模型的传统理解，以及对当前的火灾管理实践。

附：英文原文

Title: Drought triggers and sustains overnight fires in North America

Author: Luo, Kaiwei, Wang, Xianli, de Jong, Mark, Flannigan, Mike

Issue&Volume: 2024-03-13

Abstract: Overnight fires are emerging in North America with previously unknown drivers and implications. This notable phenomenon challenges the traditional understanding of the ‘active day, quiet night’ model of the diurnal fire cycle and current fire management practices. Here we demonstrate that drought conditions promote overnight burning, which is a key mechanism fostering large active fires. We examined the hourly diurnal cycle of 23,557 fires and identified 1,095 overnight burning events (OBEs, each defined as a night when a fire burned through the night) in North America during 2017–2020 using geostationary satellite data and terrestrial fire records. A total of 99% of OBEs were associated with large fires (>1,000ha) and at least one OBE was identified in 20% of these large fires. OBEs were early onset after ignition and OBE frequency was positively correlated with fire size. Although warming is weakening the climatological barrier to night-time fires, we found that the main driver of recent OBEs in large fires was the accumulated fuel dryness and availability (that is, drought conditions), which tended to lead to consecutive OBEs in a single wildfire for several days and even weeks. Critically, we show that daytime drought indicators can predict whether an OBE will occur the following night, which could facilitate early detection and management of night-time fires. We also observed increases in fire weather conditions conducive to OBEs over recent decades, suggesting an accelerated disruption of the diurnal fire cycle.

DOI: 10.1038/s41586-024-07028-5

Source: https://www.nature.com/articles/s41586-024-07028-5