Spatial and temporal variability in the ratio of trace gases emitted from biomass burning
Spatial and temporal variability in the ratio of trace gases emitted from biomass burning
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DOI：
10.5194/acp-11-3611-2011
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发表时间：
2010-10
影响因子：
6.3
通讯作者：
T. T. Leeuwen-T.;G. Werf
中科院分区：
文献类型：
--
作者：
T. T. Leeuwen-T.;G. Werf
摘要。火灾是大气中微量气体和气溶胶的主要来源。生物质燃烧的数量正变得越来越为人所知，最重要的是由于改进了燃烧面积数据集和更好地表示燃料消耗。然而，燃烧成排放的微量气体和气溶胶的生物质分配的时空变异性得到的关注相对较少。为了将燃烧的生物质转化为痕量气体和气溶胶排放，大多数研究使用了基于现场测量结果的算术平均值的排放比率（或排放因子（EFs）），并按生物群系分层。然而，即使在单一生物群系内，EFs在时间和空间上也有很大差异。此外，目前尚不清楚现有的野外测量地点是否为各种生物群系提供了具有代表性的样本。本文利用现有的生态系统文献，结合卫星获取的植被特征和气候条件信息，更好地了解生态系统的时空变化。虽然我们的研究重点是CO、ch4和CO 2，但我们的发现也适用于其他微量气体和气溶胶。我们探讨了生态效应与可能与生态效应部分变异相关的环境变量（树木覆盖密度、植被绿度、温度、降水和旱季长度）之间的关系。虽然在特定的案例研究中发现了合理的相关性，但基于全套可用测量的相关性较低，分别解释了CO、ch4、CO 2和改良燃烧效率（MCE）的33%、38%、19%和34%的变异性。这可能部分是由于环境变量的不确定性、电火花测量技术的差异、对燃烧和阴燃之间比例的假设，以及关于电火花测量地点和时间的不完整信息。我们利用与火灾排放相关的每个测量位置的相对重要性，推导出新的平均EFs。这些加权平均值与算术平均值相对相似。当利用环境变量和生态效应之间的关系外推到区域和全球尺度时，我们发现了实质性的差异，热带稀树草原的CO和ch4生态效应比实地研究的计算平均值高13%和22%，这可能与森林火灾在生态效应测量地点的代表性不足有关。我们认为，从全球建模的角度来看，如果在整个火灾季节进行测量，并且如果环境条件和EFs之间的关系得到更多关注，那么未来的测量活动可能会更有益。
Abstract. Fires are a major source of trace gases and aerosols to the atmosphere. The amount of biomass burned is becoming better known, most importantly due to improved burned area datasets and a better representation of fuel consumption. The spatial and temporal variability in the partitioning of biomass burned into emitted trace gases and aerosols, however, has received relatively little attention. To convert estimates of biomass burned to trace gas and aerosol emissions, most studies have used emission ratios (or emission factors (EFs)) based on the arithmetic mean of field measurement outcomes, stratified by biome. However, EFs vary substantially in time and space, even within a single biome. In addition, it is unknown whether the available field measurement locations provide a representative sample for the various biomes. Here we used the available body of EF literature in combination with satellite-derived information on vegetation characteristics and climatic conditions to better understand the spatio-temporal variability in EFs. While focusing on CO, CH 4 , and CO 2 , our findings are also applicable to other trace gases and aerosols. We explored relations between EFs and different measurements of environmental variables that may correlate with part of the variability in EFs (tree cover density, vegetation greenness, temperature, precipitation, and the length of the dry season). Although reasonable correlations were found for specific case studies, correlations based on the full suite of available measurements were lower and explained about 33%, 38%, 19%, and 34% of the variability for respectively CO, CH 4 , CO 2 , and the Modified Combustion Efficiency (MCE). This may be partly due to uncertainties in the environmental variables, differences in measurement techniques for EFs, assumptions on the ratio between flaming and smoldering combustion, and incomplete information on the location and timing of EF measurements. We derived new mean EFs, using the relative importance of each measurement location with regard to fire emissions. These weighted averages were relatively similar to the arithmetic mean. When using relations between the environmental variables and EFs to extrapolate to regional and global scales, we found substantial differences, with for savannas 13% and 22% higher CO and CH 4 EFs than the arithmetic mean of the field studies, possibly linked to an underrepresentation of woodland fires in EF measurement locations. We argue that from a global modeling perspective, future measurement campaigns could be more beneficial if measurements are made over the full fire season, and if relations between ambient conditions and EFs receive more attention.