Spatiotemporal variation in urban overheating magnitude and its association with synoptic air-masses in a coastal city

Urban overheating (UO) may interact with synoptic-scale weather conditions. The association between meteorological parameters and UO has already been a subject of considerable research, however, the impact of synoptic-scale weather conditions on UO magnitude, particularly in a coastal city that is also near the desert landmass (Sydney) has never been investigated before. The present research examines the influence of synoptic-scale weather conditions on UO magnitude in Sydney by utilizing the newly developed gridded weather typing classification (GWTC). The diurnal, and seasonal variations in suburban-urban temperature contrast (Delta T) in association with synoptic-scale weather conditions, and Delta T response to synoptic air-masses during extreme heat events are investigated in three zones of Sydney. Generally, an exacerbation in UO magnitude was reported at daytime over the years, whereas the nocturnal UO magnitude was alleviated over time. The humid warm (HW), and warm (W) air-masses were found primarily responsible for exacerbated daytime UO during extreme heat events and in all other seasons, raising the mean daily maximum Delta T to 8-10.5 degrees C in Western Sydney, and 5-6.5 degrees C in inner Sydney. The dry warm (DW), and W conditions were mainly responsible for urban cooling (UC) at nighttime, bringing down the mean daily minimum Delta T to - 7.5 to - 10 degrees C in Western Sydney, and - 6 to - 7.5 degrees C in inner Sydney. The appropriate mitigation technologies can be planned based on this study to alleviate the higher daytime temperatures in the Sydney suburbs.

Automated summary

The research in Sydney found that synoptic-scale weather conditions impact the magnitude of urban overheating, with daytime UO exacerbating over time and nighttime UO alleviating. Humid warm (HW) and warm (W) air masses primarily exacerbate daytime UO during extreme heat events and all other seasons, while dry warm (DW) and W conditions mainly contribute to urban cooling (UC) at nighttime. These findings suggest that appropriate mitigation technologies can be planned to alleviate higher daytime temperatures in Sydney suburbs.