In studies employing only objective thermal indices, it was found that macroclimate factors, such as the latitude, distance from the sea, and altitude, have similar contribution to the outdoor thermal comfort as microclimate factors, such as height to width ratio (H/W) and sky view factor.
For studies employing subjective thermal indices which collected participants' thermal perceptions, the neutral temperature expressed by physiologically equivalent temperature (PET) was found to be significantly correlated with macroclimate factors, especially the latitude and season. The relative importance of these influencing factors was assessed via five verified artificial neural network (ANN) models. This paper employed 43 previously published studies to comprehensively explore the impacts of macro- and micro- climatic factors on the outdoor thermal comfort. However, the combined impacts of macroclimate and microclimate factors are less understood in previous thermal comfort studies.
Outdoor thermal comfort is significantly affected by climate, including macroclimate, local climate, and microclimate. We provide new and valuable understandings to improve urban ventilation assessment in high-density cities. Finally, to balance accuracy and data availability, we recommend power law method as the optimal method to provide inflow boundary condition for numerical simulations when LiDAR observation is not available. Consequently, large deviations (> 100%) of wind-relevant criterion for outdoor thermal comfort are observed. Deviations caused by physical and empirical models are smaller but still significant (BLWT (> 25%) and PL (> 40%)). The largest deviations of wind velocity ratio are found in mesoscale meteorological models (RAMS and WRF (> 65%)). The results indicate significant deviations in LES caused by conventional methods. Large Eddie Simulations (LES) are conducted to further investigate the sensitivity of urban ventilation assessment results to the deviations of wind profiles. The evaluation involves two typical urban sites with different densities under summer weak-wind conditions. The conventional methods include Boundary Layer Wind Tunnel (BLWT), Regional Atmospheric Modeling System (RAMS), Power Law (PL), and Weather Research and Forecasting (WRF). This study uses Light Detection and Ranging (LiDAR) observation as benchmark to evaluate accuracy of wind profiles estimated by conventional methods. The vertical wind speed profile is crucial to urban ventilation assessment and urban planning/design. The returning (easterly) flow at 1.5–1.6 km was clearly observed over the sea-breeze cells. The time–height cross section of wind indicated that the top of sea (land) breeze reached a maximum height of 1.5 km (0.8 km) with maximum winds 0.4 km (0.3–0.4 km) high in the late afternoon (early morning). The sea-breeze front was identified by a steep horizontal temperature gradient, and its passage was accompanied by an abrupt temperature drop as well as vapor pressure and wind increases. The land breeze occurred within 50 km of the shoreline until noon. The resulting sea breeze began at the shoreline at 1200 local standard time (LST), moved landward at a rate of about 10 km h⁻¹, and reached 60 km from the shoreline at 1800 LST. This induced sea–land-breeze circulation. The 6-day average diurnal variations of surface meteorological variables revealed temperature differences between land and sea, driving the pressure differences between the two. These data were obtained from high-resolution surface meteorological stations and three wind lidar stations for 6 consecutive days (17–) with very weak synoptic winds and low cloud covers. In this study, detailed surface meteorological and vertical profile features about sea and land breezes in the Seoul Metropolitan Area (SMA) were investigated using the data from urban meteorological observation system in SMA (UMS-Seoul). Local circulation plays an important role in producing high-resolution meteorological and air quality information.
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