Climate Dynamics Preceding Summer Forest Fires in California and the Extreme Case of 2018
Climate Dynamics Preceding Summer Forest Fires in California and the Extreme Case of 2018
复制标题
加州夏季森林火灾前的气候动态以及 2018 年的极端情况
DOI：
10.1175/jamc-d-21-0198.1
复制
发表时间：
2022
影响因子：
3
通讯作者：
Henderson, Naomi
中科院分区：
文献类型：
--
作者：
Jacobson, Tess W.;Seager, Richard;Williams, A. Park;Henderson, Naomi
最近在加州破纪录的野火季节促使调查的气候模式，通常在异常的夏季烧毁的森林面积。使用美国林务局烧伤严重度监测趋势（MTBS）产品的烧伤面积数据和欧洲中期天气预报中心（ERA 5）在1984-2018年期间产生的第五次主要全球再分析的气候数据，前期气候异常的年际变化与7月加州烧伤面积之间的关系在空间和时间上具有特征。滞后相关表明，前期高蒸汽压赤字（VPD），高温，频繁的极端高温天，低降水，高沉降，高位势高度，低土壤湿度，低积雪和融雪异常都与7月加州烧毁面积显着相关，早在火灾季节前的1月。季节回归图表明，全球中纬度大气波列在冬末与异常7月加州烧毁面积。2018年7月，一个特别高的烧毁面积的一年，在某种程度上与回归揭示的一般模式一致：冬季降水量低，春季VPD高之前的极端烧毁面积。然而，位势高度距平模式与回归中的模式不同。7月的极端高温可能导致了当月火灾的程度，尽管7月的极端气温与7月的燃烧面积并没有显著的相关性。虽然2018年之前的气候条件是典型的高烧毁面积年份，但它们并不极端，表明极端火灾季节的统计预测可能存在的局限性，以及极端年份个别案例研究的必要性。意义陈述本研究的目的是确定前几个季节的局部和全球气候模式，这些模式影响加州夏季森林烧毁面积的变化。今年。我们发现，干燥的大气，高温，干燥的土壤，积雪少，降水少，下沉的空气，以及高气压中心以西的加州都与大面积的夏季烧毁面积显着相关，早在前一年1月。这些气候异常是半球尺度模式的一部分，与热带太平洋的联系很弱。我们还描述了2018年极端和破纪录的烧毁面积之前的气候异常，以及这些异常与发现的更普遍的模式的比较。这些结果为预测加州即将到来的夏季野火季节的严重程度提供了重要的见解。
Recent record-breaking wildfire seasons in California prompt an investigation into the climate patterns that typically precede anomalous summer burned forest area. Using burned-area data from the U.S. Forest Service’s Monitoring Trends in Burn Severity (MTBS) product and climate data from the fifth major global reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ERA5) over 1984–2018, relationships between the interannual variability of antecedent climate anomalies and July California burned area are spatially and temporally characterized. Lag correlations show that antecedent high vapor pressure deficit (VPD), high temperatures, frequent extreme high temperature days, low precipitation, high subsidence, high geopotential height, low soil moisture, and low snowpack and snowmelt anomalies all correlate significantly with July California burned area as far back as the January before the fire season. Seasonal regression maps indicate that a global midlatitude atmospheric wave train in late winter is associated with anomalous July California burned area. July 2018, a year with especially high burned area, was to some extent consistent with the general patterns revealed by the regressions: low winter precipitation and high spring VPD preceded the extreme burned area. However, geopotential height anomaly patterns were distinct from those in the regressions. Extreme July heat likely contributed to the extent of the fires ignited that month, even though extreme July temperatures do not historically significantly correlate with July burned area. While the 2018 antecedent climate conditions were typical of a high-burned-area year, they were not extreme, demonstrating the likely limits of statistical prediction of extreme fire seasons and the need for individual case studies of extreme years.Significance StatementThe purpose of this study is to identify the local and global climate patterns in the preceding seasons that influence how the burned summer forest area in California varies year-to-year. We find that a dry atmosphere, high temperatures, dry soils, less snowpack, low precipitation, subsiding air, and high pressure centered west of California all correlate significantly with large summer burned area as far back as the preceding January. These climate anomalies occur as part of a hemispheric scale pattern with weak connections to the tropical Pacific Ocean. We also describe the climate anomalies preceding the extreme and record-breaking burned-area year of 2018, and how these compared with the more general patterns found. These results give important insight into how well and how early it might be possible to predict the severity of an upcoming summer wildfire season in California.