Analysis of heat and moisture trasfer in urbanized area

在第一部分中，分析了日本气象厅和东京都政府在过去25年中每小时获得的气象数据，以检测温度和湿度的趋势。我们发现，日最低气温一直在上升，而绝对湿度最近已经停止下降或增加。为了验证城市化和年降水量对水热平衡的影响，还研究了水热年平衡。在第二部分中，我们建立了一个三维区域模型，该模型考虑了复杂的地形、土地利用、城市冠层和人为的热和水分释放。该模型由四个子模型组成。即地面热传导模型、地面热湿平衡模型、基于动量、热量和质量通量不变假设的地面层模型和求解一组方程的Ekman层模型。这里，在Ekman layr模式中，我们采用了一个修正的k-e湍流模式，以便进行稳定的统计。通过对夏季晴天的数值模拟，发现温湿度受土地利用、海风等因素的影响，人为热释放对夜间温度的影响较大，汽车和人体释放的水分对夜间温度影响较小。为了理解所涉及的水文过程，开发了一个基于物理的分布模型。该模式在玉马河中游进行了试验，并在1992~1994年应用于东京都，网格尺寸为1公里，时间步长为1小时。很明显，土地利用的变化导致了蒸散量和鲍文比的相当大的变化。

In the first part, the meteorological data obtained hourly over twenty five years by the Meteorological Agency of Japan and the Tokyo Metropolitan Government were analyzed to detect the trends in temperature and moisture. We found that the daily minimum temperature has been increasing while absolute humidity has stopped decreasing or rather increased recently. Annual balances of water and heat were also studied to confirm the effects of urbanization and annual precipitation on water and heat balances.In the second part, we developed a three-dimensional regional model that takes into account of complex topography, land use, urban canopies and anthropogenic heat and moisture release. The model is made up of four submodels. That is, a heat conduction model in ground, a heat and moisture balance model at ground surface, a surface layr model that is based on the assumption of constant momentum, heat and mass fluxes and an Ekman layr model that solves a set of equations. Here in the Ekman layr model, we adopted a k-e turbulence model modified for stable statification. Through numerical simulation for summer fine days, it is found that the temperature and humidity are affected by land use, sea breeze and that anthropogenic heat release exerts considerable influence on temperature at night while moisture release from cars and human bodies are of minor role.The third part is devoted the analysis of water and heat transfer in ground and at ground surface. A physically-based distribution model was developed to understand the hydrological processes involved. The model performance was tested in the middle reach of Tama river and then applied to Tokyo Metropolis from 1992 to 1994 with the mesh size of 1km and time step of a hour. It is made clear that the changes in land use have led to considerable change in evapotranspiration and the Bowen ratio.