Search Results (8)

Urban ventilation corridors are designed to enhance air quality, alleviate urban thermal conditions, reduce pollution and energy consumption, as well as improve human comfort within cities. They play a pivotal role in mitigating environmental impacts, particularly in densely populated urban areas. Based on satellite remote sensing data, meteorological observations, basic geographic information of Zhengzhou City and its surroundings, and urban planning data, we analyzed the urban wind environment, urban heat island, ecological cold sources, and ventilation potential. The findings reveal several key insights: (1) Dominant winds in Zhengzhou City predominantly originate from the northwest, northeast, and south, influenced by topography and the monsoon climate, with seasonal variations. These wind patterns are crucial considerations for designing primary ventilation corridors. (2) The urban heat island exhibits a polycentric spatial distribution, with intensity decreasing from the city center towards the periphery. Ecological cold sources, primarily situated in the city outskirts, act as reservoirs of fresh air that mitigate the urban heat island effect through designated corridors. (3) A preliminary corridor system, termed “eight primary and thirteen secondary corridors”, is proposed for Zhengzhou City based on an integrated assessment of ventilation potential, urban surface roughness, and sky view factor. This research contributes to advancing the understanding of urban ventilation systems and provides practical insights for policymakers, urban planners, and researchers seeking sustainable solutions to mitigate climate impacts in rapidly urbanizing environments in the region. Full article

Urban ventilation corridors (UVCs) have the potential to effectively mitigate urban heat islands and air pollution. Shanghai, a densely populated city located in eastern China, is among the hottest cities in the country and requires urgent measures in order to enhance its ventilation system. This study introduces a novel approach that integrates land surface temperature retrieval, PM_2.5 concentration retrieval, and wind field simulation to design UVCs at the city level. Through remote sensing data inversion of land surface temperature (LST) and PM_2.5 concentration, the study identifies the action spaces and compensation spaces for UVCs. The Weather Research and Forecasting (WRF) model, coupled with the multilayer urban scheme Building Effect Parameterization (BEP) model, is employed to numerically simulate and analyze the wind field. Based on the identification of thirty high-temperature zones and high PM_2.5 concentration zones as action spaces, and twenty-two low-temperature zones and low PM_2.5 concentration zones as compensation spaces in Shanghai, the study constructs seven first-class ventilation corridors and nine secondary ventilation corridors according to local circulation patterns. Unlike previous UVC research, this study assesses the cleanliness of cold air, which is a common oversight in UVC planning. Ignoring the assessment of cold air cleanliness can result in less effective UVCs in improving urban air quality and even exacerbate air pollution in the central city. Therefore, this study serves as a crucial contribution by rectifying this significant deficiency. It not only provides a fresh perspective and methodology for urban-scale ventilation corridor planning but also contributes to enhancing the urban microclimate by mitigating the effects of urban heat islands and reducing air pollution, ultimately creating a livable and comfortable environment for urban residents. Full article

SARS-CoV-2 genetic sequence results collected from native COVID-19 cases who waited or saw relatives off at Xi’an Xianyang International Airport were highly consistent with the imported cases. In order to explore the routes of transmission and influencing factors that may cause the transmission of SARS-CoV-2 at the airport, a field simulation experiment of aerosol diffusion was adopted based on epidemiological survey data and a detailed field investigation of airport structure and ventilation. The results showed that the inbound passengers waited for approximately 3 h in the rest area on the first level of the international arrival area (Zone E). During the period, masks were removed for eating and drinking, resulting in the viral aerosols rising from the first level to the second level with hot air. After deplaning, the inbound passengers handled the relevant procedures and passed through the corridor on the second floor. The local side wall of the corridor adopted fan coil air conditioning, combined with fresh air supply and personnel walking, resulting in airflow flowing to Zone E. After merging with diffused air containing virus aerosol from the first floor, it continued to spread upward to the connected third-layer area. There was a local suspended ceiling on the top of the third floor, but it was approximately 4 m high and connected to the corridor from Terminal 2 to Terminal 3. When the virus aerosol diffused above the Terminal 2–Terminal 3 corridor, where the temperature was low and the air diffused downward, it could cause an infection risk for people passing through the corridor. In addition, the investigation found that the exhaust pipes of the nucleic acid sampling rooms at the international arrival corridor were directly discharged outdoors without treatment. Only one exhaust pipe and poor ventilation in the bathroom in Zone E had a risk of viral aerosol diffusion. Therefore, the international arrival area should be set up alone or separated from the other areas by hard isolation to avoid the existence of communication between different areas that could cause viral aerosols to diffuse with airflow. The toilet ventilation should be increased to avoid the accumulation of viral aerosols at high concentrations. The exhaust pipes of the toilet and the nucleic acid sampling rooms should be equipped with disinfection and efficient filtration devices, and high-altitude emission should be adopted to reduce the risk of virus aerosol diffusion. Full article

A cross-layer non-vertical transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) occurred in a quarantine hotel in Guangzhou, Guangdong Province, China in June 2021. To explore the cross-layer transmission path and influencing factors of viral aerosol, we set up different scenarios to carry out simulation experiments. The results showed that the air in the polluted room can enter the corridor by opening the door to take food and move out the garbage, then mix with the fresh air taken from the outside as part of the air supply of the central air conditioning system and re-enter into different rooms on the same floor leading to the same-layer transmission. In addition, flushing the toilet after defecation and urination will produce viral aerosol that pollutes rooms on different floors through the exhaust system and the vertical drainage pipe in the bathroom, resulting in cross-layer vertical transmission, also aggravating the transmission in different rooms on the same floor after mixing with the air of the room and entering the corridor to become part of the air supply, and meanwhile, continuing to increase the cross-layer transmission through the vertical drainage pipe. Therefore, the air conditioning and ventilation system of the quarantine hotel should be operated in full fresh air mode and close the return air; the exhaust volume of the bathroom should be greater than the fresh air volume. The exhaust pipe of the bathroom should be independently set and cannot be interconnected or connected in series. The riser of the sewage and drainage pipeline of the bathroom should maintain vertical to exhaust independently and cannot be arbitrarily changed to horizontal pipe assembly. Full article

A wind corridor forest is defined as an urban forest for utilizing the functions of a wind corridor that allow “cool and fresh air (cold air)” generated in forests at night to flow to urban development areas. This study aims to provide planning strategies for implementing a wind corridor forest by analyzing current conditions in Haengbok City (HBC region), Sejong, South Korea. The HBC region had many wind-generating forests (WGF), wind-spreading forests (WSF), and wind-connecting forests (WCF), and secured the connections among the target areas of each wind corridor forest. Despite the favorable conditions for a wind corridor forest, cold air flow showed that there are regions with unfavorable wind conditions in the HBC region. In order to strengthen the functions of a wind corridor forests in the HBC region, four zones were distinguished according to the functional characteristics. Additionally, the planning strategies of a wind corridor forests suitable for each zone were provided, and the strategies for establishing a wind corridor forest were proposed. The results of this study can be used as the fundamental data for establishing guidelines for a wind corridor forest and utilized as resources for selecting regions suitable for a wind corridor forest. Full article

Urban ventilation corridors serve as channels of fresh air flow between the city and suburbs, helping to improve the wind and thermal environments and thermal comfort. However, owing to the limited number of weather stations, it is impossible to quantitatively reveal the effective effect range of urban ventilation corridors on urban thermal comfort at the scale of 100 × 100 m, which is optimal for urban ventilation corridors. In this study, we integrated building data, the European Centre for Medium-Range weather forecast data (ECMWF), MOD13Q1, and other multisource data to analyse the effect of urban ventilation corridors on urban thermal comfort at a unified scale of 100 × 100 m. The results showed that ECMWF and Landsat8 data could be used as substitute factors to improve the universal thermal climate index (UTCI) urban spatial resolution. The effective range of urban ventilation corridor effects on the urban surface temperature and urban comfort was ≤1000 m, with building density and vegetation coverage as the main factors limiting this range. Therefore, attention should be paid to the effective range of urban ventilation corridors, the surrounding building density, vegetation coverage, and the rational use of urban ventilation corridors to reduce the energy consumption of air conditioning in summer. Full article

City centers have to cope with an increasing amount of air pollution. The supply of fresh air is crucial yet difficult to ensure, especially under stable conditions of the atmospheric boundary layer. This case study used the PArallelized Large eddy simulation (LES) Model PALM to investigate the wind field over an urban lake that had once been built as a designated fresh air corridor for the city center of Münster, northwest, Germany. The model initialization was performed using the main wind direction and stable boundary layer conditions as input. The initial wind and temperature profiles included a weak nocturnal low-level jet. By emitting a passive scalar at one point on top of a bridge, the dispersion of fresh air could be traced over the lake’s surface, within street canyons leading to the city center and within the urban boundary layer above. The concept of city ventilation was confirmed in principle, but the air took a direct route from the shore of the lake to the city center above a former river bed and its adjoining streets rather than through the street canyons. According to the dispersion of the passive scalar, half of the city center was supplied with fresh air originating from the lake. PALM proved to be a useful tool to study fresh air corridors under stable boundary layer conditions. Full article

Glaciers in the Qilian Mountains are important sources of fresh-water for sustainable development in the Hexi Corridor in the arid northwest China. Over the last few decades, glaciers have generally shrunk across the globe due to climate warming. In order to understand the current state of glaciers in the Qilian Mountains, we compiled a new inventory of glaciers in the region using Landsat Operational Land Imager (OLI) images acquired in 2015, and identified 2748 glaciers that covered an area of 1539.30 ± 49.50 km² with an ice volume of 81.69 ± 7.40 km³, among which the Shule River basin occupied the largest portion of glaciers (24.8% in number, 32.3% in area, and 35.6% in ice volume). In comparison to previous inventories, glacier area was found to shrink by 396.89 km² (20.5%) in total, and 109 glaciers with an area of 8.94 km² disappeared over the period from the 1960s to 2015. This situation was primarily caused by the increase in air temperature, and also related with the size of glacier and some local topographic parameters. In addition, the change of glaciers in the Qilian Mountains showed a distinct spatial pattern, i.e., their shrinking rate was large in the east and small in the west. Full article