Study of heat and water-vapor transport by wind channel effect of urban river.

河流不仅是凉爽的地方，也是所谓的风道，具有缓解气候变化的作用。统计分析表明，受天气风条件的影响，海风锋对关东飞机的穿透分为东风和南风两种情况。在这两种情况下，研究了海风锋的穿透特征。特别是对典型的城市河流荒川河进行的气象场观测结果表明，该河在南风与河流流量相匹配的情况下，引导海风锋向内陆移动。在次级尺度城市周围，由于热岛的存在，海风锋面的穿透受阻，海风锋面可能被海风锋面包围。利用区域大气模拟系统(RAMS)，结合FDDA(四维数据分析)和多网格嵌套系统两种先进的气象预报技术，对沿江风场进行了数值模拟。模拟结果与现场观测结果吻合较好，较好地模拟了沿河复杂的风场。研究结果表明，其作用机理如下：1.夏季晴朗天气风平浪静时，风道效应明显。2.河流与周边地区粗糙度和热量平衡的差异对海风锋的穿透有很大的影响。3.在河流宽度较大的情况下，由于冷空气从河流平流而来，阻碍了对周围地区的渗透。4.局地风环流使污染物向河流聚集。前缘的浓度较高。

A river has the effect of climate alleviation as a not only cool spot but so called wind channel. Statistical analysis shows the penetration of sea breeze front over Kanto plane is classified into two cases, East or South-wind, influenced by synoptic wind condition. In these two cases the characteristics of the penetration of sea breeze front were investigated. Especially the result of meteorological field observation conducted along Arakawa-river, a typical urban river, shows that the river leads the sea breeze front to inland at South-wind match with river flow. Around secondary scale urban the penetration of sea breeze front are blocked over urban area because of heat island then the front may be surrounding there.Numerical simulation using RAMS (Regional Atmospheric Modeling System) including two advanced meteorological prediction techniques, FDDA (Four Dimensional Data Analysis) and Multi-grid nesting system, have been performed to investigate the wind field pattern along the river. The results agreed well with field observations, and the complex wind field along the river was simulated very well. As the results, following mechanisms were shown. 1. Wind channel effect is prominent when it is clear day and synoptic wind is calm in summer. 2. The penetration of sea breeze fronts is strongly influenced by the difference of roughness and heat balance between the river and the surrounding area. 3. In case that width of river is large, penetration at the surrounding area is blocked because the cold air is advected from river. 4. Local wind circulation accumulates the pollutants toward the river. The concentration is high at the front edge.