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首页> 外文期刊>Atmospheric chemistry and physics >Effects of lightning and other meteorological factors on fire activity in the North American boreal forest: Implications for fire weather forecasting
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Effects of lightning and other meteorological factors on fire activity in the North American boreal forest: Implications for fire weather forecasting

机译：闪电和其他气象因素对北美寒带森林火灾的影响：火灾天气预报的意义

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摘要

The effects of lightning and other meteorological factors on wildfire activity in the North American boreal forest are statistically analyzed during the fire seasons of 2000-2006 through an integration of the following data sets: the MODerate Resolution Imaging Spectroradiometer (MODIS) level 2 fire products, the 3-hourly 32-km gridded meteorological data from North American Regional Reanalysis (NARR), and the lightning data collected by the Canadian Lightning Detection Network (CLDN) and the Alaska Lightning Detection Network (ALDN). Positive anomalies of the 500 hPa geopotential height field, convective available potential energy (CAPE), number of cloud-to-ground lightning strikes, and the number of consecutive dry days are found to be statistically important to the seasonal variation of MODIS fire counts in a large portion of Canada and the entirety of Alaska. Analysis of fire occurrence patterns in the eastern and western boreal forest regions shows that dry (in the absence of precipitation) lightning strikes account for only 20% of the total lightning strikes, but are associated with (and likely cause) 40% of the MODIS observed fire counts in these regions. The chance for ignition increases when a threshold of at least 10 dry strikes per NARR grid box and at least 10 consecutive dry days is reached. Due to the orientation of the large-scale pattern, complex differences in fire and lightning occurrence and variability were also found between the eastern and western sub-regions. Locations with a high percentage of dry strikes commonly experience an increased number of fire counts, but the mean number of fire counts per dry strike is more than 50% higher in western boreal forest sub-region, suggesting a geographic and possible topographic influence. While wet lightning events are found to occur with a large range of CAPE values, a high probability for dry lightning occurs only when 500 hPa geopotential heights are above ～5700 m and CAPE values are near the maximum observed level, underscoring the importance of low-level instability to boreal fire weather forecasts.
机译：通过整合以下数据集，对2000-2006年火季期间闪电和其他气象因素对北美北方森林野火活动的影响进行了统计分析：中等分辨率成像光谱仪（MODIS）2级火产品，来自北美区域再分析（NARR）的每3小时32公里的网格化气象数据，以及加拿大闪电探测网络（CLDN）和阿拉斯加闪电探测网络（ALDN）收集的闪电数据。发现500 hPa地势高度场的正异常，对流有效势能（CAPE），云对地雷击的次数以及连续的干旱天数在统计上对MODIS火灾数的季节性变化具有重要意义。加拿大的大部分地区和整个阿拉斯加。对东部和西部北方森林地区火灾发生模式的分析表明，干燥（没有降水）雷击仅占总雷击的20％，但与MODIS关联（并可能引起）40％在这些区域观察到的火灾计数。当每个NARR网格盒的干罢工阈值至少达到10个并且连续至少10天为干日时，点燃的机会就会增加。由于大规模模式的方向，东部和西部分区之间在火灾和雷电发生以及变异性方面也存在复杂的差异。干罢工百分比较高的地区通常发生的火灾次数增加，但是在西部的北方森林次区域，每次干罢工的平均火灾次数要高出50％以上，这表明了地理和可能的地形影响。虽然发现在CAPE值范围较大时会发生湿闪电事件，但仅当500 hPa的地势高度在〜5700 m以上且CAPE值接近最大观测值时，才发生干闪电的可能性很高，这突出了低雷击的重要性。北方火灾的天气预报水平不稳定。

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