New fire diurnal cycle characterizations to improve fire radiative energy assessments made from MODIS observations
New fire diurnal cycle characterizations to improve fire radiative energy assessments made from MODIS observations
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DOI：
10.5194/acp-15-8831-2015
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发表时间：
2015-01-01
影响因子：
6.3
通讯作者：
Wooster, M. J.
中科院分区：
文献类型：
--
作者：
Andela, N.;Kaiser, J. W.;Wooster, M. J.
准确的近真实的时间火灾排放的估计是空气质量预报所必需的。迄今为止，大多数方法都是基于卫星获得的火灾辐射功率（FRP）的估计，它可以转换为火灾辐射能量（FRE），这是直接相关的火灾排放。这些森林资源估算的不确定性往往很大。这在很大程度上是因为最常用的低地球轨道卫星仪器，如中分辨率成像光谱仪，对通常明显的火灾日周期的采样相对较差。在本文中，我们探讨了空间变化的火灾日周期和驱动程序使用的数据从地球静止气象卫星旋转增强可见光和红外成像仪（SEVIRI）。此外，我们采样的数据从SEVIRI仪器在MODIS探测的机会，开发两种方法来估计每小时的FRE基于MODIS主动火灾探测。第一种方法忽略了火灾的日周期，假设持续的火灾活动之间的两个中分辨率成像光谱仪观测，而第二种方法结合知识的气候学火灾的日周期与主动火灾探测，以估计每小时的FRE。完整的SEVIRI时间序列，提供完整的覆盖范围的火灾昼夜周期，被用来评估结果。我们的研究期为3年（2010-2012），我们专注于非洲和地中海盆地，以避免使用在非常远离天底视角下获得的可能质量较低的SEVIRI数据。我们发现，火灾的日周期变化很大，在研究区域，并取决于燃料和天气条件。例如，以具有高峰火灾活动的火灾昼夜循环、白天的长持续时间和夜间火灾活动为特征的更“强烈”的火灾在大火灾规模的区域（即，大面积火灾）。这些地区在相对干旱的地区最为普遍。忽略火灾日周期通常会导致高估的FRE，而包括信息的气候学的火灾日周期改善FRE估计。基于火灾日周期的气候学知识的方法也提高了FRE在一天中的分布，虽然只有当聚集模型结果粗糙的空间和/或时间尺度良好的相关性被发现与完整的SEVIRI每小时的参考数据集。我们建议在哥白尼大气监测服务所使用的全球火灾同化系统中使用区域变化的火灾日周期信息，这将改进森林可再生能源估计数，并可能进一步协调不同清单的生物量燃烧排放估计数。
Accurate near real time fire emissions estimates are required for air quality forecasts. To date, most approaches are based on satellite-derived estimates of fire radiative power (FRP), which can be converted to fire radiative energy (FRE) which is directly related to fire emissions. Uncertainties in these FRE estimates are often substantial. This is for a large part because the most often used low-Earth orbit satellite-based instruments such as the Moderate Resolution Imaging Spectroradiometer (MODIS) have a relatively poor sampling of the usually pronounced fire diurnal cycle. In this paper we explore the spatial variation of this fire diurnal cycle and its drivers using data from the geostationary Meteosat Spinning Enhanced Visible and Infrared Imager (SEVIRI). In addition, we sampled data from the SEVIRI instrument at MODIS detection opportunities to develop two approaches to estimate hourly FRE based on MODIS active fire detections. The first approach ignored the fire diurnal cycle, assuming persistent fire activity between two MODIS observations, while the second approach combined knowledge on the climatology of the fire diurnal cycle with active fire detections to estimate hourly FRE. The full SEVIRI time series, providing full coverage of the fire diurnal cycle, were used to evaluate the results. Our study period comprised of 3 years (2010-2012), and we focused on Africa and the Mediterranean basin to avoid the use of potentially lower quality SEVIRI data obtained at very far off-nadir view angles. We found that the fire diurnal cycle varies substantially over the study region, and depends on both fuel and weather conditions. For example, more "intense" fires characterized by a fire diurnal cycle with high peak fire activity, long duration over the day, and with nighttime fire activity are most common in areas of large fire size (i.e., large burned area per fire event). These areas are most prevalent in relatively arid regions. Ignoring the fire diurnal cycle generally resulted in an overestimation of FRE, while including information on the climatology of the fire diurnal cycle improved FRE estimates. The approach based on knowledge of the climatology of the fire diurnal cycle also improved distribution of FRE over the day, although only when aggregating model results to coarser spatial and/or temporal scale good correlation was found with the full SEVIRI hourly reference data set. We recommend the use of regionally varying fire diurnal cycle information within the Global Fire Assimilation System (GFAS) used in the Copernicus Atmosphere Monitoring Services, which will improve FRE estimates and may allow for further reconciliation of biomass burning emission estimates from different inventories.