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由于现有MODIS火点检测算法对不同区域和不同季节的适应能力有限,因此需要关注复杂地表条件下对森林火灾伴生烟羽的识别问题,以提高明火点和低温焖烧火点的检测精度。本文基于烟羽扩散对大气气溶胶分布产生的影响,通过提取火灾区域的大气气溶胶光学厚度信息来描述区域内潜在火点的烟羽扩散特征,作为判识火点的辅助手段。利用MODIS资料,借助暗像元法通过6S模式反演了多个火点及周围区域的气溶胶光学厚度(AOD),并对明火点和低温火点在不同扩散范围和不同方位角条件下AOD的累积效应对烟羽的敏感性进行实验。结果表明,利用暗像元法反演出的AOD能明显地表征火灾伴生烟羽的分布特征,指示烟羽扩散方向及大致扩散范围。当以火点为中心,取32位方位角,扩散半径为10 km时,下风向与上风向的AOD累积效应差异最为显著,其累积值之比均>10,对烟羽检测最为敏感。由此建立烟羽识别条件,为判识火点提供辅助依据,有效规避了MODIS火点检测算法对离散火点,特别是低温火点的漏判。
Because existing MODIS detection algorithms have limited adaptability to different regions and seasons, it is necessary to pay attention to the recognition of forest plumes associated with forest fire under complex surface conditions in order to improve the detection accuracy of open flame and low temperature braised fire. Based on the influence of smoke plume diffusion on atmospheric aerosol distribution, the smoke aerosol diffusion characteristics of potential fire spots in the area are extracted by extracting the aerosol optical thickness information of fire area as an aid to identify fire spots. Using MODIS data, the aerosol optical depth (AOD) of multiple fire spots and surrounding areas was retrieved by 6S model by means of the dark-pixel method. The AOD of the fire point and the low-temperature fire point in different diffusion range and azimuth The cumulative effect of plume sensitivity experiments. The results show that AOD, which is derived from the dark-pixel method, can clearly characterize the distribution of fire-associated plume and indicate the direction and general diffusion range of plume. When the azimuth angle is 32 and the radius of diffusion is 10 km, the cumulative effect of AOD in the downwind and upwind directions is the most significant. The cumulative value ratio is> 10, which is most sensitive to the detection of plume. The establishment of smoke plume recognition conditions, to provide a supplementary basis for identifying fire points, effectively avoiding the MODIS fire detection algorithm for discrete fire points, especially the low temperature fire point of the leakage judgment.