Warming weakens the night-time barrier to global fire
Warming weakens the night-time barrier to global fire
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DOI：
10.1038/s41586-021-04325-1
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发表时间：
2022-02-17
期刊：
影响因子：
64.8
通讯作者：
Williams, A. Park
中科院分区：
文献类型：
--
作者：
Balch, Jennifer K.;Abatzoglou, John T.;Williams, A. Park
由于较低的温度和较低的蒸气压赤字（VPD），夜间为减缓或扑灭火灾提供了一个关键的窗口。然而，火灾危险通常是根据白天条件来评估的(1,2)，捕捉促进火灾蔓延的因素，而不是阻碍火灾的因素。尽管人们普遍认识到白天天气条件的变化会加剧火灾，但夜间条件的潜在变化及其作为减火剂的相关作用却鲜为人知。在这里，我们发现夜间火灾强度有所增加，这与更炎热和干燥的夜晚有关。我们的研究结果基于对白天和夜间火灾探测的全球卫星观测以及相应的每小时气候数据，从中我们确定了特定于土地覆盖的 VPD 阈值 (VPDt)，低于该阈值的火灾探测非常罕见（建模机会低于 95%）。在全球范围内，从 1979 年到 2020 年，每日最低 VPD 增加了 25%。在可燃土地上，每年可燃夜间时间（当 VPD 超过 VPDt 时）增加了 110 小时，使得可燃性永远不会停止的额外 5 个夜晚。在此期间，在近五分之一的可燃土地上，易燃夜晚至少增加了一周。根据卫星记录测量，从 2003 年到 2020 年，全球夜间火灾的强度增加了 7.2%。这些结果进一步说明了近年来野火扑灭小组缺乏夜间救援的情况。我们预计，人为气候变化导致的夜间持续变暖将引发更强烈、更持久和更大规模的火灾。
Night-time provides a critical window for slowing or extinguishing fires owing to the lower temperature and the lower vapour pressure deficit (VPD). However, fire danger is most often assessed based on daytime conditions(1,2), capturing what promotes fire spread rather than what impedes fire. Although it is well appreciated that changing daytime weather conditions are exacerbating fire, potential changes in night-time conditions-and their associated role as fire reducers-are less understood. Here we show that night-time fire intensity has increased, which is linked to hotter and drier nights. Our findings are based on global satellite observations of daytime and night-time fire detections and corresponding hourly climate data, from which we determine landcover-specific thresholds of VPD (VPDt), below which fire detections are very rare (less than 95 per cent modelled chance). Globally, daily minimum VPD increased by 25 per cent from 1979 to 2020. Across burnable lands, the annual number of flammable night-time hours-when VPD exceeds VPDt -increased by 110 hours, allowing five additional nights when flammability never ceases. Across nearly one-fifth of burnable lands, flammable nights increased by at least one week across this period. Globally, night fires have become 7.2 per cent more intense from 2003 to 2020, measured via a satellite record. These results reinforce the lack of night-time relief that wildfire suppression teams have experienced in recent years. We expect that continued night-time warming owing to anthropogenic climate change will promote more intense, longer-lasting and larger fires.