Quantifying the microclimatic feedback of citywide rooftop photovoltaic deployment in Sendai, Japan

Rooftop photovoltaic (PV) deployment supports urban decarbonization, but its local microclimatic effects and interactions with urban morphology remain underexplored, particularly in coastal cities such as Sendai, Japan. The current study uses the weather research and forecasting (WRF) model with PV parameterization scheme and local climate zone (LCZ) data at 400 m resolution to conduct five experiments (exp_ctrl, exp_25, exp_50, exp_75, and exp_100) representing 0–100% citywide PV roof coverage during the hottest week of 2025. PV deployment produced a discernible, spatially heterogeneous cooling effect, with mean surface air temperature reductions of 0.03–0.06 °C by day and 0.07–0.14 °C at night, alongside minor localized warming (< 0.08 °C) during morning and evening transitions. Higher-coverage scenarios reduced specific humidity by 70.8% (exp_75) and 62% (exp_100) of the day. Ground and sensible heat fluxes declined by up to 11.8 and 21.7 W/m 2 as coverage increased, while latent heat flux changes remained minor, indicating that PV roofs cool mainly by reducing heat storage rather than by evapotranspiration. All scenarios lowered the mean boundary layer height by up to 79.4 m. Compact mid- and low-rise zones showed the strongest cooling and highest electricity yields, whereas compact high-rise zones warmed slightly under higher coverage. Mean electricity output rose linearly with coverage, reaching 151 Wh/m 2 per day and 66.5 g CO₂ m -2 per day savings at full deployment. These results indicate that moderate, LCZ-specific PV coverage, rather than full saturation, offers the best balance of cooling, energy generation, and climate resilience to guide effective PV deployment policy in cities.