The Effect of Urban Canyon Morphology on Urban Heat Island Mitigation in Amman City: A Comparative Analysis of Downtown and Al Abdali

Urban heat island (UHI) mitigation in semi-arid cities depends partly on urban canyon geometry, yet urban canyon-scale empirical evidence from Middle Eastern contexts remains limited. This study quantified how urban canyon morphology influences near-surface air temperature and outdoor thermal comfort in Amman, Jordan, using six representative urban canyons in Downtown and Al Abdali. A mixed-methods framework combined GIS-based morphology extraction (height-to-width ratio, H/W; sky view factor, SVF; and urban canyon orientation) with field measurements of air temperature, relative humidity, and wind speed at pedestrian height, recorded from 08:00 to 00:00 during June 2023. Thermal comfort was assessed using the Universal Thermal Climate Index (UTCI), and relationships between morphology and microclimate were examined using regression analysis. The most open urban canyon (A1; H/W = 0.65, SVF = 0.60, NW–SE) recorded the highest mean air temperature (29.0°C) and a peak of 32.8°C, whereas the deepest urban canyon (B3; H/W = 5.2) recorded the lowest mean air temperature (27.1°C). H/W showed a strong inverse association with air temperature across both areas (pooled R² = 0.6331). SVF explained 56% of the pooled temperature variance (R² = 0.5628), but the direction of association differed by area (positive in Downtown and negative in Al Abdali), indicating context dependence and co-variation with other geometric controls. Wind speed showed negligible explanatory power in the pooled dataset (R² = 0.0013). Overall, the results highlight urban canyon depth and shading geometry as key urban-design levers to reduce daytime heat exposure and support UHI-oriented mitigation strategies in Amman.