植生への粒子沈着モデルの研究動向とその課題

概要

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Recent progress in modeling particle deposition onto vegetation and the issues in validating these models are described in the present paper. Comparisons of size-dependent deposition velocity between calculations and observations may not be sufficient to validate individual modeled processes incorporated in the particle deposition model. The differences of environmental factors between measurements and calculations should be taken into account to validate the modeled processes depending on particle size ranges. Numerical simulations using detailed one-dimensional atmosphere-soil-vegetation model including particle deposition onto vegetation (SOLVEG) developed by the authors was carried out. The model reproduced the measured turbulent fluxes over the coniferous forest canopies for large (> 1 µm) and fine (< several 100 nm) particles. For the sub-micron particles, however, our model underestimated the measured particle deposition velocity obtained from various campaigns. Electrostatic deposition, thermo- and diffusio-phoretic deposition, micro-roughness such as cilium at the leaf surface, and particle growth under humid environment could affect particle deposition in this size range. Vegetation parameters such as Leaf Area Index (LAI) and leaf width also have a significant effect on the deposition velocity. This effect should be incorporated into future parameterizations of particle deposition velocity onto vegetation.