Fire radiative energy for quantitative study of biomass burning: derivation from the BIRD experimental satellite and comparison to MODIS fire products
Fire radiative energy for quantitative study of biomass burning: derivation from the BIRD experimental satellite and comparison to MODIS fire products
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DOI：
10.1016/s0034-4257(03)00070-1
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发表时间：
2003-06-30
影响因子：
13.5
通讯作者：
Oertel, D
中科院分区：
文献类型：
--
作者：
Wooster, MJ;Zhukov, B;Oertel, D
全球变化研究的一个主要重点是量化陆地植被火灾排放的气体和颗粒污染物的数量。确定生物质燃烧过程中释放的辐射能（所谓的火辐射能或FRE）已被建议作为确定生物质燃烧速率和大气污染物产生速率变化的新工具。我们回顾了远程测定FRE的物理原理，并提出了一种替代方法，通过分析中红外光谱区的“火像素”辐射率来推导FRE。我们比较我们的方法，现有的FRE检索方法中使用的EOS中分辨率成像光谱辐射计（MODIS）火灾产品，并检索FRE的基础上派生的火灾温度和面积通过所谓的双光谱方法。我们测试每一个FRE检索方法，使用模拟数据和图像从一个新的实验空间使命，双光谱红外探测（BIRD）小卫星，它有专门设计用于研究活跃的火灾传感器。我们分析近同时的MODIS和BIRD数据的火灾，在2002年1月澳大利亚悉尼附近燃烧。尽管这些传感器的像素大小和光谱覆盖范围有显着不同，其中由MODIS和BIRD检测到的火灾像素组的空间范围是相似的，这些火灾的FRE的派生值同意在+/-15%。然而，在某些火灾中，较低的空间分辨率的中分辨率成像光谱仪似乎阻止了许多不太强烈的辐射火灾像素被检测到，这意味着中分辨率成像光谱仪低估了这些火灾的FRE高达46%相比，鸟。虽然这些低强度火像素中的每一个的FRE释放相对较低，但是它们的相对较大的数量使得它们的总体FRE显著。因此，2002年1月5日悉尼大火的总FRE释放量通过BIRD估计为6.5 x 10（9）J s（-1），但通过MODIS估计为4.0 x 10（9）J s（-1）。BIRD分辨单个火锋的能力进一步允许通过星载测量首次精确计算“辐射”火线强度，为长度达9 km的火锋提供15-75 kJ s（-1）m（-1）的值。最后，我们分析了基于卫星的FRE检索方法的有效性，估计FRE从活跃的燃烧和阴燃组件（FREActive，被认为是成比例的生物质燃烧率），尽管传感器接收额外的辐射从“冷却地面”。在这方面，MIR辐射率方法显得特别强大，允许在100- 100，000 J s（-1）m（-2）范围内将FREActive估计为+/- 30%。这些结果提供了进一步的信心，在空间飞行任务的能力，以获得物理意义的价值，可用于支持生物质燃烧排放清单的森林资源。未来的比较FRE来自通过MODIS和那些从更高的空间分辨率BIRD或机载图像可能允许的MODIS派生的FRE值进行“校准”的任何系统低估。因此，我们期望FRE成为一个重要的工具，以加强全球研究的陆地植被火灾与红外遥感，特别是因为大多数大型火灾现在每天四次成像通过中分辨率成像分光仪仪器的Terra和Aqua航天器。(C)2003年爱思唯尔科学公司All rights reserved.
A major focus in global change research is to quantify the amount of gaseous and particulate pollutants emitted from terrestrial vegetation fires. Determination of the emitted radiant energy released during biomass combustion episodes (the so-called fire radiative energy or FRE) has been suggested as a new tool for determining variations in biomass combustion rates and the rate of production of atmospheric pollutants. We review the physical principals behind the remote determination of FRE and present an alternative method for its derivation via analysis of 'fire pixel' radiances in the middle infrared spectral region. We compare our method to the existing FRE retrieval approach used in the EOS Moderate Resolution Imaging Spectro-radiometer (MODIS) fire products, and to retrievals of FRE based on derived fire temperature and area made via the so-called Bi-spectral method. We test each FRE retrieval method using both simulated data and imagery from a new experimental space mission, the Bi-spectral InfraRed Detection (BIRD) small satellite, which has sensors specifically designed for the study of active fires. We analyse near simultaneous MODIS and BIRD data of the fires that burned around Sydney, Australia in January 2002. Despite the markedly different pixel size and spectral coverage of these sensors, where the spatial extent of the fire pixel groups detected by MODIS and BIRD are similar, the derived values of FRE for these fires agree to within +/- 15%. However, in certain fires, the lower spatial resolution of MODIS appears to prevent many of the less intensely radiating fire pixels being detected as such, meaning MODIS underestimates FRE for these fires by up to 46% in comparison to BIRD. Though the FRE release of each of these low intensity fire pixels is relatively low, their comparatively large number makes their overall FRE significant. Thus, total FRE release of the Sydney fires on 5 January 2002 is estimated to be 6.5 x 10(9) J s(-1) via BIRD but 4.0 x 10(9) J s(-1) via MODIS. The ability of BIRD to resolve individual fire fronts further allows the first accurate calculation of 'radiative' fireline intensity from spaceborne measurements, providing values of 15-75 kJ s(-1) m(-1) for fire fronts that are up to 9 kin in length. Finally, we analyse the effectiveness of the satellite-based FRE retrieval methods in estimating the FRE from the active flaming and smouldering components only (FREActive, believed to be proportional to the rate of biomass combustion), despite the sensor receiving additional radiance from the 'cooling ground'. The MIR radiance method appears particularly strong in this regard, allowing FREActive to be estimated to within +/- 30% in the range 100-100,000 J s(-1) m(-2). These results provide further confidence in the ability of spacebome missions to derive physically meaningful values of FRE that could be used to support biomass burning emissions inventories. Future comparisons between FRE derived via MODIS and those from higher spatial resolution BIRD or airborne imagery may allow the MODIS-derived FRE values to be 'calibrated' for any systematic underestimation. We therefore expect FRE to become an important tool for enhancing global studies of terrestrial vegetation fires with infrared remote sensing, particularly as the majority of large fires are now imaged four times per day via the MODIS instruments on the Terra and Aqua spacecraft. (C) 2003 Elsevier Science Inc. All rights reserved.