摘要
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。
The limitation of existing MODIS fire detection algorithm appears when it is applied to monitor forest fires in different season or in different regions. In response to these problems,the smoke plume identification in forest fires over complex surface types is studied to improve detection ability of open flame fire spots and cool smouldering fire spots. According to the effect of smoke plume diffusion on atmospheric aerosol distribution,a detection method for the smoke plume is offered as potentiating tools to identify fire pixels by extracting atmospheric Aerosol Optical Depth( AOD) information from fire areas. Based on the 6S( Second Simulation of a Satellite Signal in the Solar Spectrum) radioactive transfer model,the Dark Target( DT) method is used to retrieve AOD form M ODIS data in many fire spots and background areas. In addition,the sensitivity of AOD cumulative effect to the smoke plume diffusion in different azimuth directions and different diffusion ranges is discussed. The results showthat AOD retrieved by DT method could stand for the distribution characters of smoke volume,as well as indicate the direction and the rough range of smoke spread. The values of AOD in 32 azimuth directions are accumulated when the distance from the centre is 10 km,if the true fire spots are thought as the centre of a circle. The most remarkable difference of AOD cumulative value is found by comparing the leeward side to the windward side. The ratio of the two is more than ten to one. So it will provide an effective auxiliary criterion for MODIS fire detection algorithm to avoid missing disperse fire spots,especially cool fire spots.
出处
《高原气象》
CSCD
北大核心
2015年第3期797-803,共7页
Plateau Meteorology
基金
国家重点基础研究发展规划项目(2011CB706903)
中国气象局大气探测重点开放实验室开放课题(KLAS201408)
关键词
森林火灾
气溶胶光学厚度
烟羽检测
Forest fires
Aerosol Optical Depth(AOD)
Smoke plume detection
