Impact of Building Structure on Heat Storage Flux Estimation: An Observational Case Study in Beijing

Abstract

The urban heat storage flux, $Q_{\mathrm {S}}$ , is one of the main drivers of the nocturnal urban heat island effect. However, the complex 3-D building structure makes observations and simulations of $Q_{\mathrm {S }}$ difficult. This study observes the 3-D surface radiant temperature ( $T_{\mathrm {s}}$ ) of a building in Beijing, China. The element surface temperature method (ESTM) and the half-order (HO) method are compared for $Q_{\mathrm {S}}$ simulation using $T_{\mathrm {s}}$ observations. The impact of building structure on $Q_{\mathrm {S}}$ and urban heat island intensity (UHII) are also studied. Results show the following. First, $Q_{\mathrm {S}}$ 's simulated by ESTM and HO are nearly the same for walls. However, the HO method only needs one-layer exterior surface temperature, which has great potential for regional $\Delta Q_{\mathrm {S}}$ simulation by satellite remote sensing data. Second, during the daytime, $Q_{\mathrm {S}}$ 's of each facet are significantly different from each other. The maximum observed difference of $Q_{\mathrm {S}}$ is up to 452 W/m2 between the roof and north wall in May 2019. Third, complete $Q_{\mathrm {S}}$ ( $Q_{\mathrm {S, c}}$ ) is calculated by each facet $Q_{\mathrm {S}}$ and area fraction. The relationships between UHII and both 2-D $Q_{\mathrm {S}}$ (roof $Q_{\mathrm {S}}$ ) and 3-D $Q_{\mathrm {S }}(Q_{\mathrm {S, c}})$ are studied. $Q_{\mathrm {S}}$ is positively correlated with nocturnal UHII, and 3-D $Q_{\mathrm {S}}$ corresponds more closely to UHII with a larger Spearman's coefficient ( $p < 0.05$ ). This study presents the effect of building structure on heat flux and could provide an insight for future $Q_{\mathrm {S}}$ and urban heat island (UHI) studies.