Spatial planning for urban ventilation corridors by urban climatology

Ventilation corridors in cities can decrease air pollution and alleviate heat island problems but there remains a need to fully assess their effectiveness.Few urban managers have been able to take city-scale approaches to the construction of urban ventilation corridors.This study aimed to introduced the Ventilation Corridor Planning(VCP)model,which is a multi-criteria evaluation method combined with a geographical information system(GIS)to determine where the ventilated environment is most appropriate.Specifically,the VCP model took Bozhou,China as the research object and contained two scales,including mesoscale and local scale.In mesoscale scale,we got three outputs to build urban ventilation corridors,including 1)background wind environment,2)ventilation potential,3)heat island intensity.In local scale,we used traditional computational fluid dynamics(CFD)model to verify the impact of VCP criteria.The results revealed that compared with the traditional CFD model,the proposed VCP model has advantages in establishing a comprehensive evaluation standard.In addition,the application of VCP model in macro and micro also enhances the efficiency of ventilation corridor construction.Overall,this study introduced a effective modeling method to urban ventilation corridors planning,and provide a way to study the urban climate.

ON TEMPERATURE CHANGES OF SHANGHAI AND URBANIZATION IMPACTS

To understand how temperature varies in urban Shanghai under the background of global climate change and how it is affected by urbanization, the Shanghai temperature responses to global warming were analyzed, and then the temperature trends of urban and suburb stations under different climatic backgrounds were obtained. The urbanization effects on temperature were studied by comparing urban stations to suburb stations, the relationship between urbanization variables and temperature components were obtained, and observation data of surface and high level were combined to assess the contribution of urbanization effect. In the last part of the paper, the cause of urbanization effects on temperature was discussed. The results indicated: The long term change trend of Shanghai annual mean temperature is 1.31/100a from 1873 to 2004, the periods of 1921 – 1948 and 1979 – 2004 are warmer, and the 1979 – 2004 period is the warmest; compared to suburb stations, the representative urban station has slower decreases in the cool period and faster increases in the warm one; the urban and suburb temperatures have distinct differences resulting from urbanization and the differences are increasing by the year, with the difference of mean temperature and minimum temperature being the greatest in fall and that of maximum temperature being the largest in summer between the urban and suburban areas. The urbanization process accelerates the warming speed, with the minimum temperature being the most obvious; the urbanization effect contributes a 0.4°C increase in 1980s and 1.1°C in 1990s to the annual mean temperature.

Microclimatic Experimentation Applied to Insulating Horizontal Coverage in Mexicali, Mexico

The thermal response of hedges alters the urban climate, resulting in energy and comfort affectations that impact city dwellers, so the aim of this study is to analyze the energy fluxes of urban horizontal coverage, especially expanded polystyrene waterproofed with elastomeric paint in the city of Mexicali, Baja California, located northwest of Mexico. The experiment was realized on summer of 2011 and 2012 by using four components radiometric sensor, eddy covariance equipment, which was possible to analyze the behavior and intensities of heat fluxes using the model Q＊ = QE ＋ QG ＋ QH ＋ QF ＋ QD. The results show that in both campaigns the sensible heat flux exceeds the net radiation, in 2011 the net radiation was 31.41 W/mE and sensible heat flux of 74.9 W/m2, in 2012 resulted 43.46 W/m2 and 87.32 W/mE, respectively. This additional heat flux is attributed to the thermal influence of the air conditioning units, which changes the energy balance model to Q＊ = QH ＋ QF ＋ QD. With the results arise the need for experimentation on a larger scale in which it is possible to model the flow in housing development. The knowledge of the energy balance model will help to propose materials that minimize the thermal impact to the city of Mexicali.