  Urban heat island (UHI) in conjunction with heatwave (HW) leads to
exacerbation of thermal stress in urban areas. Prior research on UHI and HW has
predominantly concentrated on examining the thermal conditions at the surface
and near-surface, with few investigations extending to the radiative and
dynamical interactions of UHI and HW, particularly with a focus on the
inhomogeneities across local climate zones (LCZs). Here, we analyse the
temperature disparity between HW and non-HW conditions across LCZs in the
Sydney area by quantifying the contributions of individual radiative and
dynamical processes using the coupled surface-atmosphere climate
feedback-response analysis method (CFRAM). Three HW events in 2017, 2019, and
2020 are simulated using the Weather Research and Forecasting (WRF) model
coupled with the Single-Layer Urban Canopy Model (SLUCM). The maximum
temperature difference between HW and non-HW days may reach up to 10 K, with
the increased net solar radiation during HWs being comparable to the typical
level of anthropogenic heat flux in urban areas. It is also found that the
reduction of clouds, the presence of vapor, and the increase of sensible heat
contribute to the warming effect at different levels, with the contribution of
clouds being the most dominant. Conversely, the generation of dry convection
and the increase of latent heat flux lead to mitigating effects, with the
latter being more dominant and capable of causing up to 10 K surface
temperature difference between LCZ1 (compact high-rise) and LCZ9 (sparsely
built). The differences in the contributions of climate feedback processes
across different LCZs become more evident during more severe and humid HWs.
These findings underscore the necessity of implementing local climate
zone-tailored heat mitigation strategies.
