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Sea breezes are important in a coastal urban climate; however, the impact of urban development on the effects of sea breezes, which decrease air temperature and increase humidity, has not been understood quantitatively. To quantitatively evaluate this impact in Sendai, Japan over the past twenty years, this study analyzed the heat balance mechanisms in urban spaces based on the simulation results of the Weather Research and Forecasting (WRF) model coupled with Local Climate Zone (LCZ) maps. Compared to the observation data on air temperature, specific humidity, and wind in August 2002, results of the numerical simulation, using the 2002 LCZ map and the meteorological conditions of August 2002, confirmed that the WRF model could reproduce meteorological factors well. Thereafter, two numerical simulations using the LCZ maps from 2002 and 2022 were conducted based on the same meteorological condition, from 25 July to 1 September 2008, to extract the impact of urban development on the effects of sea breeze. Consequently, when land use changed from urban built-up land to natural land cover, both the effects of sea breeze—decreasing air temperature and increasing humidity—decreased. Additionally, increases in LCZ 3 (compact low rise), mainly from LCZ 6 (open low rise) and LCZ 9 (sparsely built), decreased the effects of sea breeze (decreasing air temperature and increasing humidity) by 5% and 10%, respectively, in areas around Sendai Station. This was because the consumption of the sea breeze's potential to decrease air temperature and increase humidity increased and the wind speed of sea breezes decreased in the windward areas of Sendai Station. These results provide new insights into the impact of urban development on the effects of sea breeze and quantitatively reveal changes in the effects of sea breeze. [ABSTRACT FROM AUTHOR]

• Specific UCPs and vehicle heat were integrated in WRF/BEP-BEM model over Sendai. • Profiles of hourly vehicle heat for LCZs were figured out via open-source data. • Effects of various urban heat countermeasures analyzed at a high spatial resolution • Eliminating the vehicle heat contribute up to 0.12°C to urban heat mitigation. Studies have been conducted globally on urban heat countermeasures utilizing Weather Research and Forecasting (WRF) numerical modeling system. Yet, the effects of vehicle heat (VH) on near-surface air temperature in Japanese cities were not clarified. In this study, the WRF Building Effect Parameterization and Building Energy Model (BEP-BEM) coupled with local climate zones (LCZs) was adopted for simulating the influences of VH on the urban climate over Sendai, Japan. To do so, we proposed a novel method to estimate the hourly VH for LCZs via open-source data. Integrating VH and specific urban canopy parameters (UCPs) into BEP-BEM, the climate model was established and then validated with the observed data. Based on that, effects of various urban heat countermeasures were analyzed at a high spatial resolution. It was found that eliminating the vehicle heat contributes up to 0.12°C to urban heat mitigation, as the most effective countermeasures for the compact areas of city center. This study provided a feasible and reliable workflow to quantitatively evaluate urban heat mitigation strategies at high spatial resolution, specifically for reducing VH in Japanese cities, that can support related urban planners and decision makers for implementing targeted urban heat mitigation strategies. [ABSTRACT FROM AUTHOR]

• The WUDAPT L0 method was used to classify LCZ types in Sendai, a typical Japanese metropolitan city, and the OA of our LCZ classification was 92.59 % using an independent dataset. • Both surface and ambient urban heat island analysis based on LCZ classes with GIS-based detected geometric and land cover properties are made. • LCZ map was found to be generally consistent with land surface temperature(LST) distribution but not match well with air temperature distribution. • By dividing Sendai into two regions along its urban center, the mitigating effects of sea-land breeze on the magnitudes of UHIs in each urban-rural area were demonstrated. • This study confirmed that the LCZ scheme can be used by urban planners to assess both surface UHI (SUHI) and UHI effects, and proposed a feasible process for developing targeted UHI mitigation strategies. The Local Climate Zone (LCZ) scheme is an urban form and land cover/land use classification system used to study urban heat islands (UHIs). Many studies have evaluated the relationship between LCZs and air temperature. While the intensity and spatial pattern of an UHI can be influenced by the land-sea breeze, especially in coastal cities, few studies have been done to examine this using the LCZ scheme. In this study, Sendai, Japan, has been selected as a case study to evaluate whether the LCZ scheme can be used to study UHIs that are exposed to sea-land breeze since it has two urban-rural areas: mountain side and coastal side. UHI analysis was based on LCZ classes with GIS-derived geometric and land cover properties. By dividing Sendai into two regions along its urban center, the mitigating effects of sea-land breeze on the magnitudes of UHIs in each urban-rural area were demonstrated. Based on the results of this study, two specific UHI mitigation strategies were proposed for Sendai. This study confirmed that the LCZ scheme can be used by urban planners to assess both surface UHI (SUHI) and UHI effects, and proposed a feasible process for developing targeted UHI mitigation strategies. [ABSTRACT FROM AUTHOR]