A field study on Ground Energy Balance calculation for typical communities in South China

Abstract

Urban heat island (UHI) greatly influences human health, comfort and building energy. The ground temperature plays an important role in understanding UHI, and the method based on the ground energy balance (GEB) is fundamental in the predictions of urban ground temperature and UHI. South China is fast developed and highly urbanized, with special humid subtropical climate and particular urban design characteristics. Although amounts of methods or formulas have been previously proposed for urban GEB calculation, few of them has been testified in field in South China. In this study, two typical urban communities in South China in the aligned and enclosed layout were measured during the summer sunny days in Aug. 2017, with the focus on incident solar radiation, sensible heat, and latent heat of the ground. The measured data were compared with the calculated ones by various methods. The results show that the two calculation methods, i.e., with and without reflections, showed comparable performances (difference on RMSE 3-13 W/m2) in the prediction of solar radiation incident into the community ground. The previously proposed formulas performed poorly in the prediction of surface convective heat transfer coefficient for the community hard pavement, and the power function regressed by using the measuring data performed well, with the air speed at the reference height of 0.13 m as variable and R2 of 0.74. The Bowen ratio method performed better in the prediction of latent heat for the community permeable sidewalk, with RMSE of 156 W/m2 and the consistency index of 0.93. This study provides the field evidences and reliable methods for urban GEB calculation, and potentially contributes to the UHI prediction and mitigation in South China.

Assessment of Outdoor Pedestrian Ventilation Performance While Controlling Building Array Scale and Density

“…Three approaches are typically used for urban ventilation research: wind-tunnel experiments, field measurements, and computational fluid dynamics (CFD) simulations. Field measurements usually require the arrangement of wind speed measurement points at the research objects (such as street valleys and residential areas) and comparisons of the wind speed and direction with the data of nearby weather stations [13,59]; based on these, the influence of the built environment on the wind speed can be determined. During the test, if the reference measurement point can be selected in a nearby unobstructed location, then it is generally better than the weather station measurement point as the reference point.…”