Observations of Sweep–Ejection Dynamics for Heat and Momentum Fluxes during Wildland Fires in Forested and Grassland Environments
Observations of Sweep–Ejection Dynamics for Heat and Momentum Fluxes during Wildland Fires in Forested and Grassland Environments
复制标题
森林和草原环境野火期间热和动量通量的扫射动力学观测
DOI：
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发表时间：
2021
影响因子：
3
通讯作者：
X. Bian
中科院分区：
文献类型：
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作者：
W. Heilman;T. Banerjee;C. Clements;K. Clark;S. Zhong;X. Bian
低层大气边界层中热量和动量的垂直湍流传递是通过与湍流上升气流和下降气流相关的间歇性扫掠、喷射、向外相互作用和向内相互作用事件来完成的。这些事件，统称为扫射动力学，已被广泛研究，在森林和非森林环境中，并在文献中报道。然而，鲜为人知的是，发生在响应湍流制度引起的野火在森林和非森林环境中的扫射动力学。本研究试图填补一些知识空白，通过分析湍流数据收集在三个荒地（规定）火灾发生在得克萨斯州和新泽西的草原和森林环境。基于塔的高频（10或20 Hz）三维风速和温度测量被用来检查发生的频率的扫描，喷射，向外的相互作用，向内的相互作用事件和它们的实际贡献的平均垂直湍流通量的热量和动量之前，期间，和之后的火锋的通道。观测结果表明，在这些环境中的荒地火灾可以大大改变通常发生在没有火灾时的湍流热和动量通量的扫描喷射动力学，特别是扫描与喷射在确定整体热和动量通量的相对贡献。
The vertical turbulent transfer of heat and momentum in the lower atmospheric boundary layer is accomplished through intermittent sweep, ejection, outward interaction, and inward interaction events associated with turbulent updrafts and downdrafts. These events, collectively referred to as sweep–ejection dynamics, have been studied extensively in forested and nonforested environments and reported in the literature. However, little is known about the sweep–ejection dynamics that occur in response to turbulence regimes induced by wildland fires in forested and nonforested environments. This study attempts to fill some of that knowledge gap through analyses of turbulence data previously collected during three wildland (prescribed) fires that occurred in grassland and forested environments in Texas and New Jersey. Tower-based high-frequency (10 or 20 Hz) three-dimensional wind-velocity and temperature measurements are used to examine frequencies of occurrence of sweep, ejection, outward interaction, and inward interaction events and their actual contributions to the mean vertical turbulent fluxes of heat and momentum before, during, and after the passage of fire fronts. The observational results suggest that wildland fires in these environments can substantially change the sweep–ejection dynamics for turbulent heat and momentum fluxes that typically occur when no fires are present, especially the relative contributions of sweeps versus ejections in determining overall heat and momentum fluxes.