Trees have a large role in improving urban air quality, among other mechanisms, through dry deposition of scalars and aerosols on leaf surfaces. We tested the role of leaf density and canopy structure in modulating the rate of dry deposition. We simulated the interactions between a virtual forest patch and deposition rate of an arbitrary scalar using the Parallelized Large Eddy Simulation Model (PALM). Two canopy structures were considered: a homogenous canopy and canopy stripes. For each canopy stripe scenario, we considered thin, intermediate, and wide stripes, while the space between stripes equals the stripes’ width. Four leaf area densities were considered for each case (LAI = 0.5, 1, 1.5, and 2). The results showed that denser canopies and canopy stripes experienced more total deposition, noting that stripes had a larger per leaf area deposition than homogeneous canopies. Our results can be explained by canopy-induced turbulence structures that couple the air within and above the canopy and lead to more effective leaf area where this coupling is stronger. We aggregate our results to the whole-patch scale and suggest a canopy-structure and leaf-area dependent correction to the canopy resistance parameter so to be used in coarse models that resolve dry deposition.

树木通过将标量和气溶胶干沉降在叶片表面上，在改善城市空气质量等方面发挥着重要作用。我们测试了叶密度和冠层结构在调节干沉降速率中的作用。我们使用并行大涡模拟模型（PALM）模拟了虚拟森林斑块与任意标量沉积速率之间的相互作用。考虑了两个冠层结构：同质冠层和冠层条纹。对于每种冠层条纹方案，我们考虑了细，中和宽条纹，而条纹之间的间距等于条纹的宽度。对于每种情况，考虑了四个叶面积密度（LAI = 0.5、1、1.5和2）。结果表明，密实的树冠和树冠条纹经历了更多的总沉积，注意条纹比同质树冠的每叶面积沉积更大。我们的结果可以通过冠层诱发的湍流结构来解释，该湍流结构将冠层内部和顶部的空气耦合，并导致更有效的叶面积，这种耦合更强。我们将结果汇总到整个补丁规模，并建议对冠层阻力参数进行冠层结构和叶面积相关的校正，以便用于解决干沉降的粗糙模型中。