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

河流不仅是凉爽的地方，而且是所谓的风道，具有缓解气候的作用。统计分析表明，海风锋在关东平面上的穿透受天气风条件的影响，可分为东风和南风两种情况。在这两种情况下，海风锋的穿透特性进行了研究。特别是对典型的城市河流荒川的沿着气象观测结果表明，荒川在南风时与河流的水流相匹配，引导海风锋向内陆移动。利用区域大气模拟系统RAMS（Regional Atmospheric Modeling System）结合FDDA（Four-Dimensional Data Analysis）和多重网格嵌套系统（Multi-grid Nesting System）两种先进的气象预报技术，对长江沿岸沿着风场进行了数值模拟。模拟结果与实测结果吻合较好，并较好地模拟了沿着复杂的风场。研究结果表明，其作用机理如下：1.夏季晴天、天气风平静时，风道效应显著。2.海风锋的穿透强烈地受到河流和周围地区之间的粗糙度和热平衡的差异的影响。3.如果河流的宽度很大，则由于冷空气从河流平流进入，因此阻碍了周围地区的渗透。4.当地的风循环使污染物向河流聚集。在前边缘处浓度高。

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.