The Relationship Between Urban Spatial Morphology Parameters and Urban Heat Island Intensity Under Fine Weather Condition

Urban heat island (UHI) phenomenon has a significant negative impact on economic development, urban climate, human life and health. An important cause for UHI is that intense buildings block the radiative transfer and exchange between urban canopies. Building distribution patterns and heights, which affect the formation and intensity of urban heat island, can be described with urban morphological parameters including frontal area index (FAI) and sky view factor (SVF).With high spatial resolution, 3D building data of Adelaide central city, Australia, SVF and FAI are estimated and their relationships with urban heat island intensity (UHII) under fine weather conditions are analyzed. Sky view factor is a commonly-used morphological parameter that describes the degree to which the sky is obscured by building block. Compared with sky view factor calculated from fish-eye photos, SVF is very consistent with the former, with the correlation coefficient of 0.97, which can be used to analyze the change of urban heat island intensity in different seasons. Frontal area index is calculated by weighted average method of all seasons with observations of wind speed and direction in Adelaide airport. Relationships between SVF and UHII, FAI and UHII in different times of various seasons and their influences are analyzed.A high negative linear relationship is found between SVF and UHII at night time under fine weather conditions, and significant positive linear relationship is found during daytime, especially in the afternoon of spring, autumn and winter. A logarithmic relationship is found between FAI and UHII appears at night and morning time, while at daytime they are linearly related. The applicability of the correlation between SVF and UHII at different search radius is higher than that of FAI. At the scale of 200 m, at night time of spring and winter, the correlation of FAI and UHII is greater than that of SVF and UHII, while the correlation between SVF and UHII is greater at daytime of autumn. For the other moments, there are little difference between correlation of FAI to UHII and that of SVF to UHII.