## 3 Measurement Results and Discussion
### Summer Season Experiments
#### 3.1.3 Analysis Results and Discussion
This suggests that the observed reduction in direct sunlight to the ground due to the reduction in Ginza had little effect on lowering the temperature of the ground. In Daimon, there were few buildings, but the area occupied by plants was large, reducing the sky's area, which in turn reduced the negative far-infrared energy and increased the positive radiation energy from the plants to the human body. The difference with Ginza was that the ground radiation energy at visible and near-infrared wavelengths was also significantly reduced, even though the area occupied by the ground was almost the same. In Ginza, there could be the case that light reflected from the buildings may have been directed to the ground, but the absorption and diffuse reflection of sunlight by the plants largely blocked the sunlight from reaching the ground in Daimon. As a result, the heat load from the ground to the human body at far-infrared wavelengths was reduced. As a countermeasure against UHI, the use of vegetation [8; 10] and highly reflective paints [31; 32] on the ground, buildings, and other structures is often considered. By blocking sunlight from reaching the ground with vegetation, the temperature of the ground can be lowered, and the heat load of far-infrared radiation from the ground to the human body can be reduced. However, the energy radiated from the human body to the sky will also be reduced, which may result in an increase in the far-infrared heat load on the human body. This can be expected from comparing the results of the Imperial Palace and Daimon. On the other hand, the effect of vegetation is also to reduce the heat load in visible and near-infrared wavelengths from the sky and ground. In addition to the radiation heat transfer, vegetation can play a role in cooling through the transpiration effect, in which plants evaporate and transpire simultaneously. The energy consumed during evapotranspiration plays a role in lowering the temperature of the air around the plants. The use of highly reflective paints should be carefully considered. The use of highly reflective paints on buildings increases the amount of energy that is reflected by the building and directed toward the ground or the human body. In addition, the reflected radiation from the building will heat the ground, increasing the radiation from the ground at far-infrared wavelengths. Therefore, the use of paints that increase reflectivity may increase the heat load on the human body. The reflectance of asphalt, a typical ground material, is about 5% [33]. If this reflectance is simply increased several times, it means that the visible and near-infrared heat loads will also increase several times, although the far-infrared heat load will decrease due to the lower ground temperature. As with vegetation, it is a complex phenomenon that needs to be considered in conjunction with changes in atmospheric temperature due to changes in the temperature of various structures. From the viewpoint of heat load due to radiation, it is important to consider the direction in which radiation from the sun is reflected. Recent research has been conducted on paints that enable retroreflections [34], which will play an important role in counteracting UHI.