A methodology for evaluation of vertical dispersion and dry deposition of atmospheric aerosols
A methodology for evaluation of vertical dispersion and dry deposition of atmospheric aerosols
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DOI：
10.1029/2011jd016366
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发表时间：
2012-01-10
影响因子：
4.4
通讯作者：
Sofiev, Mikhail
中科院分区：
文献类型：
--
作者：
Kouznetsov, Rostislav;Sofiev, Mikhail
本文提出了一种处理大气气溶胶垂直扩散和干沉降的新方法，并初步应用于中尺度到全球大气输送模式。垂直交换方案扩展了前面为气态物质和细气溶胶所作的阻力类比。该方法是基于有限层内的气溶胶通量的稳态方程的精确解。通量表示为浓度的线性函数在层边界和帐户的垂直不均匀性的扩散系数和常规的垂直速度。新的干沉积方案考虑了气流、表面和沉积颗粒的物理性质。通过交换系数和表面特征速度的垂直剖面给出了流动。通过求解颗粒质量的预算方程，得到了光滑表面的沉积速率。从光滑到粗糙的流动状态的过渡。粗糙表面有两个尺度：气动粗糙度和“聚集尺度”。收集尺度包括收集器的有效尺寸和粗糙元件顶部的气流速度与摩擦速度的比率。粒子由它们的物理尺寸、弛豫时间和布朗扩散率描述。该方案是完全基于风洞和数值实验从文献中，并再现他们很好。室外实验的数据有明显较大的不确定性，这使得他们的协议与预测的一般评价。
A new approach to treatment of vertical dispersion and dry deposition of atmospheric aerosols is suggested for primary application in mesoscale to global atmospheric transport models. The vertical exchange scheme extends the resistance analogy formulated earlier for gaseous species and fine aerosols. The approach is based on the exact solution of the steady-state equation for aerosol flux within a finite layer. The flux is expressed as a linear function of concentrations at the layer boundaries and accounts for the vertical inhomogeneity of the diffusion coefficient and the regular vertical velocity. The new dry deposition scheme accounts for physical properties of the air flow, surface and depositing particles. The flow is given by the vertical profile of exchange coefficient and characteristic velocity at the surface. The deposition rate to smooth surfaces is obtained via solution of the budget equation for particle mass. The transition from smooth to rough flow regime is considered. Rough surfaces are characterized by two length scales: the aerodynamic roughness and the "collection scale", introduced in this paper. The collection scale incorporates the effective size of collectors and a ratio of the airflow velocity at the top of the roughness elements to the friction velocity. The particles are described by their physical size, relaxation time and Brownian diffusivity. The scheme was developed basing exclusively on wind-tunnel and numerical experiments available from the literature, and reproduces them well. The data of outdoor experiments have noticeably larger uncertainties, which allowed only general evaluation of their agreement with the predictions.