Observational and analytical studies on influence of urban surface structure on radiation balance components

研究了城市地表结构对地表辐射平衡分量变化的影响。特别是，本研究旨在通过基于热图像分析的屏蔽效应，即屏蔽因子和表面温度来解释城市表面障碍物产生的额外长波辐射。主要研究结果如下：(1)提出了城市及周边地区夜间长波辐射场的基本概念。(2)利用关东地区各城市的鱼眼镜头图像，估算了屏幕因子（即墙视因子）的水平分布。结果表明，建成区的屏蔽系数约为10 ~ 75%。(3)对某结构简单的砌体桥墩用砂岩的岩面温度进行了热图像分析，得到了充分的结果。因此，热示踪测量可以有效地用于研究城市峡谷壁面温度的实际状态和更自然的模式。(4)采用热像分析的方法，对某多户住宅冬季墙体表面温度的增温进行了研究，讨论了房间采暖和太阳辐射对其增温的影响。结果表明：太阳辐射对墙体的加热效果优于窗户，而室内采暖对窗户的加热效果优于墙壁，两者所增加的辐射（4 ~ 26w /m2）很大程度上取决于表面障碍物的附加长波辐射。(5)各长波辐射平衡分量随屏蔽系数几乎呈线性变化。很明显，如果基于热图像分析在三种不同材料中分别估计城市表面障碍物的表面温度，则从其屏效应可以充分估计城市表面障碍物的额外长波辐射。(6)城市峡谷内白天长波附加辐射比夜间增加更多，但净辐射由于太阳辐射遮阳效应的减弱而减少。街道上的遮荫树减轻了所有的辐射成分。少

Influence due to urban surface structure on the change of radiation balance components in the groundsurface is investigated. In paticular, this study aims at explaining additional longwave radiation from urban surface obstructions by their screen- effects, namelly their screen-factors and surface temperatures based on thermal image analysis. The main results are summarized as follows : (1) The fundamental concept of longwave radiation field at night is proposed in and around urban areas. (2) The horizontal distributions of screen-factor (namelly, wall view-factor) are estimated from a fish-eye lens image in various cities of Kanto region. It is shown that the screen-factor in built-up area is about 10 - 75%. (3)Thermal image analysis is tried on rock-surface temperature of sandstone used for a masonry bridge pier with simple structure, and sufficient results are obtained. Therefore, thermotracer measurement can be applied usefully to investigate the actual states of wall surface temper … More ature pattern in urban canyon. (4) The warming of wall surface temperature in winter is investigated in a maltiple dwelling house by thermal image analysis, and the influences of room heating and solar radiation on its warming are discussed. The results show that solar radiation heats more effectively wall than windowpane and roomheating heats more effectively windowpane than wall, and the increased radiation (4-26W/m2) by the both heating effects are attached great importance to additional longwave radiation from surface obstructions. (5) Every longwave radiation balancecomponent changes almost lineally with the screen-factor. It becomes clear that additional longwave radiation from urban surface obstructions is sufficiently estimated from their screen-effects, if their surface temperatures are estimated separately in three different materials based on thermal image analysis. (6) In the daytimes within urban canyon, additional longwave radiation increases more than at night, but net radiation decreases due to the shade-effective decrease of solar radiation. Street shade trees mitigate all radiation components. Less