Abstract
Air temperature is an important physical indicator for urban and architectural environments; however, it is difficult to obtain its distributive characteristics by field measurements owing to the limitations of current measuring instruments. In this context, this study was conducted to demonstrate whether a small and portable ground-based thermal infrared spectroradiometer can be used to estimate the horizontal air temperature distribution in built spaces. For this estimation, we first calculated a forward model using radiative transfer simulations, and the air temperature distribution was inversely estimated from the observed radiance using the model. To regularize the estimated air temperature, we used the maximum a posteriori method, which uses prior information. To verify this estimation method, we conducted measurement experiments in two types of built spaces that had different air temperature distributions within spaces that were approximately 20 m long. Moreover, we conducted a parametric case study on the prior information. As a result, we were able to estimate the air temperature distribution with an average root mean square error (RMSE) of 1.3 °C for all cases when the average RMSE of the prior information for all cases was 2.1 °C. This improvement in the RMSE indicates that this method is able to remotely estimate the horizontal air temperature distribution in built spaces.
Highlights
Air temperature is an important physical indicator that influences the design and functionality of urban and built environments
Of the prior information for all cases was 2.1 °C, whereas the estimated air temperature distribution was 1.3 °C, thereby indicating that the root mean square error (RMSE) of the estimated air temperature distribution was reduced by 0.8 °C
From the results of our experiments, we found that the RMSEs of the estimated air temperature were reduced when compared with those of the prior distribution, even for the relatively short paths of dozens of meters assumed in built spaces when using the thermal infrared spectroradiometer (Table 3)
Summary
Air temperature is an important physical indicator that influences the design and functionality of urban and built environments. Determining the horizontal distribution of air temperature is an important subject of research In these spaces, even if they are relatively small, the presence of a sensible heat source/sink can cause large air temperature differences. In buildings, depending on the location of the air conditioning vents, a large air temperature distribution is generated in the room (e.g., Huang et al [5] reported a temperature irregularity of approximately 2.4 °C), which affects the comfort of the occupants. Another example of a large indoor temperature distribution is that at a data center [6].
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