Seasonal Changes in Urban PM2.5 Hotspots and Sources from Low-Cost Sensors
PM2.5 concentrations in urban areas are highly variable, both spatially and seasonally. To assess these patterns and the underlying sources, we conducted PM2.5 exposure measurements at the adult breath level (1.6 m) along three ~5 km routes in urban districts of Mainz (Germany) using portable low-cost Alphasense OPC-N3 sensors. The survey took place on five consecutive days including four runs each day (38 in total) in September 2020 and March 2021. While the between-sensor accuracy was tested to be good (R² = 0.98), the recorded PM2.5 values underestimated the official measurement station data by up to 25 µg/m3. The collected data showed no consistent PM2.5 hotspots between September and M…
Modeling impacts of super cool roofs on air temperature at pedestrian level in mesoscale and microscale climate models
Abstract Passive daytime radiative cooling is gaining increasing relevance as recent studies report that newly developed materials with very high reflectivity and emissivity could be able to effectively reduce urban heat stress, when applied as roofing material (super cool roofs). A recent microscale sensitivity study with ENVI-met modeled the impact of super cool roofs with maximum air temperature reductions of around 0.85 K at pedestrian level for an idealized model area. To verify these findings in real urban structures featuring complex building morphologies and varying meteorological conditions, we conducted climate simulations for two contrasting cities: New York City, NY, and Phoenix…
Modeling the outdoor cooling impact of highly radiative “super cool” materials applied on roofs
Abstract Highly reflective “cool materials” are commonly used to reduce temperatures in the urban environment. Recently developed “super cool” materials feature an even higher albedo and emissivity (both above 0.95) than traditional cool materials. To examine the impacts of super cool roofing materials on outdoor air temperature compared to traditional cool roofs and green roofs, we conduct a sensitivity study with the microclimate model ENVI-met. Simulated surface temperature of super cool roofs remained around 6 K below ambient air temperature during high solar irradiation, which is consistent with observations. Super cool roofs – with an averaged street-level air temperature cooling of a…
Evaluating the thermal-radiative performance of ENVI-met model for green infrastructure typologies: Experience from a subtropical climate
Abstract Microclimate knowledge has been intensively integrated into urban planning and design to improve the buildings’ energy performance and outdoor thermal comfort. To assess the climatic mitigation strategies, numerical modeling is gaining higher relevance. ENVI-met, a microclimate model to simulate the complex surface-vegetation-atmosphere interactions in the built environment, is receiving increasing popularity. This study aims to systematically evaluate the thermal-radiative performance of the ENVI-met model based on its recent updates. First, a field measurement was conducted in a subtropical city. Thermal-radiative parameters were collected besides three green infrastructure (GI) …