SMOKE-COLUMN OBSERVATIONS FROM 2 FOREST-FIRES USING DOPPLER LIDAR AND DOPPLER RADAR
SMOKE-COLUMN OBSERVATIONS FROM 2 FOREST-FIRES USING DOPPLER LIDAR AND DOPPLER RADAR
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DOI：
10.1175/1520-0450(1992)031
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发表时间：
1992-11-01
期刊：
影响因子：
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通讯作者：
POST, MJ
中科院分区：
文献类型：
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作者：
BANTA, RM;OLIVIER, LD;POST, MJ
为了证明主动遥感系统在观察森林火柱行为方面的有用性，我们研究了两次火灾，一次使用3.2厘米波长的多普勒雷达，另一次更广泛地使用多普勒激光雷达。两种仪器都观察了对流柱的运动，包括两种不同类型的柱旋转，并监测了烟羽的行为。第一场火灾是一场失去控制的森林大火，是在上午晚些时候和下午被多普勒雷达观测到的。强烈的水平环境风产生了一个弯曲的对流柱，雷达观察到它的边缘有强烈的水平流动，而沿羽流中心线的流动较弱。这种速度模式表明，该柱由一对反向旋转的水平涡旋（卷）组成，沿中心线上升，沿边缘下降。雷达追踪到烟羽超过30公里。它还提供了圆形去极化比的测量结果，该数据提供的信息表明，散射粒子在雷达上大多是扁平的或针状的，可能是松针，也可能是扁平的灰片。多普勒激光雷达在5小时内观察到的第二次火灾是在下午点燃的规定森林火灾。在火灾发生的第一个小时，激光雷达观测到对流柱的许多运动学量，包括气流辐合和近垂直柱的反气旋全柱旋转，涡度约为10(-2)s-1，估计峰值垂直速度w为15 m s-1。第1小时环境气象条件改变后，全柱旋转停止，对流柱和烟羽向激光雷达倾斜，水平气流增强。在这一后期，两次估计w为24和10 m s-1。激光雷达观测显示，第二次火灾的烟羽最初在对流柱中直接上升到2 km以上的高度，因此大部分烟雾被注入到不稳定、下午、对流边界层或混合层以上的大气中。后来，随着水平风的增加，更多的烟雾留在混合层中。最后，在下午很晚的时候，在点火停止，火在闷烧之后，几乎所有的烟雾都留在了混合层中。这些分析表明，激光雷达和雷达可以提供有关火灾附近运动量和烟雾分布的有价值的三维数据集。这类信息对于理解和模拟对流柱动力学和烟羽行为具有重要价值。
To demonstrate the usefulness of active remote-sensing systems in observing forest fire plume behavior, we studied two fires, one using a 3.2-cm-wavelength Doppler radar, and one more extensively, using Doppler lidar. Both instruments observed the kinematics of the convection column, including the presence of two different types of rotation in the columns, and monitored the behavior of the smoke plume.The first fire, a forest fire that burned out of control, was observed by the Doppler radar during late-morning and afternoon hours. Strong horizontal ambient winds produced a bent-over convection column, which the radar observed to have strong horizontal flow at its edges and weaker flow along the centerline of the plume. This velocity pattern implies that the column consisted of a pair of counterrotating horizontal vortices (rolls), with rising motion along the centerline and sinking along the edges. The radar tracked the smoke plume for over 30 km. It also provided circular depolarization ratio measurements, which gave information that the scattering particles were mostly flat or needle shaped as viewed by the radar, perhaps pine needles or possibly flat ash platelets being viewed edge on.The second fire, observed over a 5-h period by Doppler lidar, was a prescribed forest fire ignited in the afternoon. During the first hour of the fire the lidar observed many kinematic quantities of the convection column, including flow convergence and anticyclonic whole-column rotation of the nearly vertical column, with a vorticity of approximately 10(-2) s-1 and an estimated peak vertical velocity w of 15 m s-1. After the first hour ambient meteorological conditions changed, the whole-column rotation ceased, and the convection column and smoke plume bent over toward the lidar in stronger horizontal flow. At two times during this later stage, w was estimated to be 24 and 10 m s-1. Lidar observations show that the smoke plume of this second fire initially went straight up in the convection column to heights of over 2 km, so most of the smoke was injected into the atmosphere above the unstable, afternoon, convective boundary layer or mixed layer. Later, as the horizontal winds increased, a larger fraction of the smoke remained in the mixed layer. Finally, very late in the afternoon, after ignitions had ceased and the fire was smoldering, almost all of the smoke remained within the mixed layer.These analyses show that lidar and radar can provide valuable three-dimensional datasets on kinematic quantities and smoke distribution in the vicinity of fires. This kind of information should be of great value in understanding and modeling convection-column dynamics and smoke-plume behavior.