Meteorological and geographical factors associated with dry lightning in central and northern California
Meteorological and geographical factors associated with dry lightning in central and northern California
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DOI：
10.1088/2752-5295/ac84a0
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发表时间：
2022-08
期刊：
影响因子：
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通讯作者：
D. Kalashnikov;J. Abatzoglou;Nicholas J. Nauslar;D. L. Swain;D. Touma;Deepti Singh
中科院分区：
文献类型：
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作者：
D. Kalashnikov;J. Abatzoglou;Nicholas J. Nauslar;D. L. Swain;D. Touma;Deepti Singh
闪电发生在小于2.5毫米的闪电-通常被称为“干闪电”-是中部和北方加州野火点燃的主要来源。尽管很罕见，但由于密集干燥的植被和大量人口居住在易发生火灾的土地附近，干闪电的爆发导致了该地区的破坏性火灾。由于雷暴在该地区相对于西部内陆要少得多，因此在加州中部和北方，干闪电的气候学和驱动因素尚未得到广泛研究。利用每日网格闪电和降水观测（1987-2020年）结合大气再分析，我们的特征干闪电的气候学和相关的气象条件在温暖的季节（5月至10月），野火的风险是最高的。在整个领域，在研究期间，所有云对地闪电中有近一半（约46%）是干闪电。我们发现，高海拔（>2000米）接收更多的干闪电相比，低海拔（<1000米），活动集中在7月至8月。虽然当地的气象条件显示出很大的空间变化，我们发现区域范围内的增强对流层中层水分和不稳定的干闪电天相对于背景气候。此外，地面温度，低对流层干燥，对流层中部的不稳定性增加整个地区的干燥与潮湿的闪电天。我们还确定了广泛的干闪电爆发的历史记录，量化其季节性和空间范围，并分析相关的大规模大气模式。这四种大气模式中有三种的特点是大陆内部的脊和近海槽的不同配置。了解该地区干闪电的气象学可以为预测可能的野火点火提供信息，并与评估气候预测中干闪电和野火风险的变化有关。
Lightning occurring with less than 2.5 mm of rainfall—typically referred to as ‘dry lightning’—is a major source of wildfire ignition in central and northern California. Despite being rare, dry lightning outbreaks have resulted in destructive fires in this region due to the intersection of dense, dry vegetation and a large population living adjacent to fire-prone lands. Since thunderstorms are much less common in this region relative to the interior West, the climatology and drivers of dry lightning have not been widely investigated in central and northern California. Using daily gridded lightning and precipitation observations (1987–2020) in combination with atmospheric reanalyses, we characterize the climatology of dry lightning and the associated meteorological conditions during the warm season (May–October) when wildfire risk is highest. Across the domain, nearly half (∼46%) of all cloud-to-ground lightning flashes occurred as dry lightning during the study period. We find that higher elevations (>2000 m) receive more dry lightning compared to lower elevations (<1000 m) with activity concentrated in July-August. Although local meteorological conditions show substantial spatial variation, we find regionwide enhancements in mid-tropospheric moisture and instability on dry lightning days relative to background climatology. Additionally, surface temperatures, lower-tropospheric dryness, and mid-tropospheric instability are increased across the region on dry versus wet lightning days. We also identify widespread dry lightning outbreaks in the historical record, quantify their seasonality and spatial extent, and analyze associated large-scale atmospheric patterns. Three of these four atmospheric patterns are characterized by different configurations of ridging over the continental interior and offshore troughing. Understanding the meteorology of dry lightning across this region can inform forecasting of possible wildfire ignitions and is relevant for assessing changes in dry lightning and wildfire risk in climate projections.