Global fire emissions and the contribution of deforestation, savanna, forest, agricultural, and peat fires (1997-2009)
Global fire emissions and the contribution of deforestation, savanna, forest, agricultural, and peat fires (1997-2009)
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DOI：
10.5194/acp-10-11707-2010
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发表时间：
2010-01-01
影响因子：
6.3
通讯作者：
van Leeuwen, T. T.
中科院分区：
文献类型：
--
作者：
van der Werf, G. R.;Randerson, J. T.;van Leeuwen, T. T.
新的燃烧区域数据集和大气中热原气体浓度测量自上而下的限制减少了火灾排放估算的巨大不确定性。然而，我们对森林砍伐、稀树草原、森林、农业废弃物和泥炭火灾对全球火灾排放总量的贡献的理解仍然存在重大差距。在这里，我们使用了卡耐基-艾姆斯-斯坦福方法（CASA）生物地球化学模型的修订版，并改进了卫星估算的燃烧面积、火灾活动和植物生产力，以0.5度的空间分辨率和每月的时间步长计算了1997-2009年期间的火灾排放量。2000年11月以后的估计是基于燃烧面积、主动火灾探测和中分辨率成像光谱辐射计（MODIS）传感器的植物生产力。对于分区，我们主要关注MODIS时代。我们使用了来自热带降雨测量任务（TRMM）可见光和红外扫描仪（VIRS）和沿着轨道扫描辐射计（ATSR）的火灾数据（1997-2000）的燃烧面积图，以及来自同期先进甚高分辨率辐射计（AVHRR）观测的植物生产力估计。根据第3版全球火灾排放数据库（GFED3）， 1997-2001年全球平均火灾碳排放量为2.0 PgC年（-1），年际变化显著（1998年为2.8 PgC年（-1），2001年为1.6 PgC年（-1））。在全球范围内，2002-2007年期间的排放量相对稳定（每年约2.1 Pg C(-1)），随后在2008年（每年1.7 Pg C(-1)）和2009年（每年1.5 Pg C(-1)）下降，部分原因是南美洲和热带亚洲的森林砍伐火灾排放量减少。在区域基础上，2002-2007年期间的排放量变化很大（例如，北方亚洲、南美洲和印度尼西亚），但这些区域差异在全球水平上相互抵消。在MODIS时代（2001-2009年），大部分碳排放来自草原和稀树草原的火灾（44%），热带森林砍伐和退化火灾（20%）、林地火灾（主要局限于热带地区，16%）、森林火灾（主要在温带地区，15%）、农业废弃物燃烧（3%）和热带泥炭火灾（3%）的贡献较小。农业废弃物火灾的贡献可能是一个下限，因为我们测量燃烧面积的方法无法检测到所有这些相对较小的火灾。总碳排放量比我们之前（GFED2）的工作平均降低了13%。对于减少的微量气体，如CO和CH4，森林砍伐、退化和泥炭火灾是更重要的贡献者，因为与稀树草原火灾相比，每单位碳燃烧减少的微量气体排放量更高。热带森林砍伐、退化和泥炭地火灾造成的碳排放量平均为每年0.5 Pg C（-1）。这些火灾产生的碳排放可能无法通过火灾后的再生来平衡。我们的研究结果首次对过去十年不同来源对全球火灾排放总量的贡献进行了全球评估，并为社区提供了改进的13年火灾排放时间序列。
New burned area datasets and top-down constraints from atmospheric concentration measurements of pyrogenic gases have decreased the large uncertainty in fire emissions estimates. However, significant gaps remain in our understanding of the contribution of deforestation, savanna, forest, agricultural waste, and peat fires to total global fire emissions. Here we used a revised version of the Carnegie-Ames-Stanford-Approach (CASA) biogeochemical model and improved satellite-derived estimates of area burned, fire activity, and plant productivity to calculate fire emissions for the 1997-2009 period on a 0.5 degrees spatial resolution with a monthly time step. For November 2000 onwards, estimates were based on burned area, active fire detections, and plant productivity from the MODerate resolution Imaging Spectroradiometer (MODIS) sensor. For the partitioning we focused on the MODIS era. We used maps of burned area derived from the Tropical Rainfall Measuring Mission (TRMM) Visible and Infrared Scanner (VIRS) and Along-Track Scanning Radiometer (ATSR) active fire data prior to MODIS (1997-2000) and estimates of plant productivity derived from Advanced Very High Resolution Radiometer (AVHRR) observations during the same period. Average global fire carbon emissions according to this version 3 of the Global Fire Emissions Database (GFED3) were 2.0 PgC year(-1) with significant interannual variability during 1997-2001 (2.8 Pg C year(-1) in 1998 and 1.6 PgC year(-1) in 2001). Globally, emissions during 2002-2007 were relatively constant (around 2.1 Pg C year(-1)) before declining in 2008 (1.7 Pg C year(-1)) and 2009 (1.5 Pg C year(-1)) partly due to lower deforestation fire emissions in South America and tropical Asia. On a regional basis, emissions were highly variable during 2002-2007 (e. g., boreal Asia, South America, and Indonesia), but these regional differences canceled out at a global level. During the MODIS era (2001-2009), most carbon emissions were from fires in grasslands and savannas (44%) with smaller contributions from tropical deforestation and degradation fires (20%), woodland fires (mostly confined to the tropics, 16%), forest fires (mostly in the extratropics, 15%), agricultural waste burning (3%), and tropical peat fires (3%). The contribution from agricultural waste fires was likely a lower bound because our approach for measuring burned area could not detect all of these relatively small fires. Total carbon emissions were on average 13% lower than in our previous (GFED2) work. For reduced trace gases such as CO and CH4, deforestation, degradation, and peat fires were more important contributors because of higher emissions of reduced trace gases per unit carbon combusted compared to savanna fires. Carbon emissions from tropical deforestation, degradation, and peatland fires were on average 0.5 Pg C year(-1). The carbon emissions from these fires may not be balanced by regrowth following fire. Our results provide the first global assessment of the contribution of different sources to total global fire emissions for the past decade, and supply the community with an improved 13-year fire emissions time series.