Abstract This study aims to develop a high-resolution forecast model for airborne birch pollen concentration in Sapporo. Using results that shows that the bulk of pollen grains was deposited near the source plant, we created a high-resolution birch tree density map from a field survey along public roads and footpaths and Street View on Google Maps. The map was linearly extrapolated to cover an area 10 km from the city centre, including forests in the south and southwest. A new atmospheric dispersion deposition model for birch pollen was developed to represent wind advection, turbulent mixing, and convection in the atmospheric boundary layer, and gravitational settling and scavenging with precipitation. Pollen emission was also modelled as a function of the birch tree density and surface air temperatures. The onset of the pollen season was based on the pollen observations by a sampler at Hokkaido Institute of Public Health in Sapporo, and the end of pollen season was assumed to be 40 days after its onset. Comparison with observations suggested that the hindcast simulation with the model reproduced the daily variations in the dry deposition well in most years from 2001 to 2011. The geographical distribution of birch pollen deposition was highly correlated with the birch tree density map, even on windy days.

中文翻译：

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札幌桦树花粉高分辨率预测系统

摘要 本研究旨在开发一种高分辨率的札幌桦树花粉浓度预测模型。使用表明大部分花粉粒沉积在源植物附近的结果，我们根据公共道路和人行道沿线的实地调查以及谷歌地图上的街景创建了高分辨率的桦树密度图。该地图被线性外推，覆盖距离市中心 10 公里的区域，包括南部和西南部的森林。开发了一种新的桦树花粉大气弥散沉积模型，以表示大气边界层中的风平流、湍流混合和对流，以及降水的重力沉降和清除。花粉排放也被建模为桦树密度和地表气温的函数。花粉季节的开始是基于札幌北海道公共卫生研究所的采样员对花粉的观察，花粉季节的结束被假定为开始后 40 天。与观测结果对比表明，该模型的后报模拟再现了2001-2011年大部分年份干沉降井的日变化。桦树花粉沉降的地理分布与桦树密度图高度相关，即使在刮风的日子。