Is 3D building morphology really related to land surface temperature? Insights from a new homogeneous unit

Exploring the effect of building morphology on Land Surface Temperature (LST) has received surging attention. In this process, a fundamental precondition is selecting an appropriate spatial statistical unit to calculate building morphological indices and corresponding LST. However, different units lead to divergent results, indicating they inevitably suffer from the Modifiable Areal Unit Problem (MAUP), which brings large uncertainties. This study places special emphasis on proposing a new spatial unit, the Homogenous Unit of Building Morphology (HUBM), to re-describe building morphology and re-analyze its effect on LST with less uncertainty. Results show: (1) building morphology portrayed by HUBM maintains more spatial characteristics and remains relatively stable across scales, which is more consistent with the realistic building environment. (2) The relationship identified by HUBM shows building morphology is not strongly correlated with LST in essence and is regarded as more authentic due to the more objective portrayal of building morphology, while this relationship may be overestimated by previous common units. (3) The effect of building morphology on LST explored by HUBM also remains relatively stable across different scales (R² fluctuation amplitude of 0.08, 0.12, and 0.08 in the spring, summer, and winter, respectively) compared to regular grids (R² fluctuation amplitude of 0.18, 0.2, and 0.2), effectively alleviating the uncertainty associated with the MAUP. These findings provide new insights into re-examining the authentic effect of building morphology on LST, assisting in addressing urban heat island effects and promoting sustainable urban development. Moreover, HUBM can be applicable to other urban issues for mitigating MAUP.