Effects of Live Fuel Moisture Content on Wildfire Occurrence in Fire-Prone Regions over Southwest China
Effects of Live Fuel Moisture Content on Wildfire Occurrence in Fire-Prone Regions over Southwest China
复制标题
西南地区火灾多发区生物质水分含量对野火发生的影响
作者：
Luo Kaiwei;Quan Xingwen;He Binbin;Yebra Marta
以往的研究表明，可燃物水分含量（LFMC）是影响全球野火发生的重要驱动因素，但在中国西南生态系统中，LFMC对野火发生的驱动作用尚未得到研究。为此，我们利用中分辨率成像光谱仪（ModerateResolutionImagingSpectrometer，MODIS）反射率产品中的物理辐射传输模型（PhysicalRadiativeTransferModel，RTM）反演的10年LFMC动态和从MODIS燃烧区（BurnedArea，BA）产品中提取的野火事件，探讨了中国西南亚热带高原区（SubtropicalHighland，Cwa）和湿润亚热带区（HumidSubtropicalZone，Cwo）森林/草原火灾发生与LFMC的关系。对火灾前LFMC和累积燃烧面积的统计结果表明，Cwa具有明显的火灾前LFMC临界阈值森林、草地和草地分别为151.3%、123.1%和51.4%和138.1%、72.8%和13.1（森林115.0%、54.4%;草地137.5%、69.0%、10.6%）。低于这些阈值，火灾发生率和燃烧面积显著增加。此外，在2009/2010年和2015/2016年火季分别发生的丘北森林火灾和灯笼山草原火灾这两起大型火灾事件发生前，LFMC动态有显著下降趋势。火灾前达到的最小LFMC值（49.8%和17.3%）接近我们报告的森林（51.4%）和草地（13.1%）的最低临界LFMC阈值。进一步的LFMC趋势分析显示，2009/2010年和2015/2016年火灾季节的区域中值LFMC动态也明显低于该地区的10年LFMC。因此，这项研究表明，LFMC动力学解释了野火发生在这些火灾多发地区在中国西南地区，允许开发一个新的业务野火危险预测模型在这一地区考虑卫星派生的LFMC产品的可能性。
Previous studies have shown that Live Fuel Moisture Content (LFMC) is a crucial driver affecting wildfire occurrence worldwide, but the effect of LFMC in driving wildfire occurrence still remains unexplored over the southwest China ecosystem, an area historically vulnerable to wildfires. To this end, we took 10-years of LFMC dynamics retrieved from Moderate Resolution Imaging Spectrometer (MODIS) reflectance product using the physical Radiative Transfer Model (RTM) and the wildfire events extracted from the MODIS Burned Area (BA) product to explore the relations between LFMC and forest/grassland fire occurrence across the subtropical highland zone (Cwa) and humid subtropical zone (Cwb) over southwest China. The statistical results of pre-fire LFMC and cumulative burned area show that distinct pre-fire LFMC critical thresholds were identified for Cwa (151.3%, 123.1%, and 51.4% for forest, and 138.1%, 72.8%, and 13.1% for grassland) and Cwb (115.0% and 54.4% for forest, and 137.5%, 69.0%, and 10.6% for grassland) zones. Below these thresholds, the fire occurrence and the burned area increased significantly. Additionally, a significant decreasing trend on LFMC dynamics was found during the days prior to two large fire events, Qiubei forest fire and Lantern Mountain grassland fire that broke during the 2009/2010 and 2015/2016 fire seasons, respectively. The minimum LFMC values reached prior to the fires (49.8% and 17.3%) were close to the lowest critical LFMC thresholds we reported for forest (51.4%) and grassland (13.1%). Further LFMC trend analysis revealed that the regional median LFMC dynamics for the 2009/2010 and 2015/2016 fire seasons were also significantly lower than the 10-year LFMC of the region. Hence, this study demonstrated that the LFMC dynamics explained wildfire occurrence in these fire-prone regions over southwest China, allowing the possibility to develop a new operational wildfire danger forecasting model over this area by considering the satellite-derived LFMC product.