Numerical modeling of the distinct urbanization impact over Singapore during two contrasting weather scenarios

Urban growth over Singapore is noticeable with increase in built-up area and significant sprawling with more than two-fold growth. Effects of urbanization patterns are investigated in two scenarios named as dry and wet, during the inter-monsoon period under high convective and low advection conditions. Weather Research and Forecasting model has been used with a finer resolution. Urban effects have been incorporated by coupling a single-layer urban canopy model. Four main experiments are designed: CTRL, SURB, NURB and HURB. CTRL uses near-realistic land-use, SURB hosts the asymmetric land-use with urban areas in south and east, NURB contains urbanization in the northern parts and HURB has homogeneous land-use. The dry case shows nocturnal southward passage of a land-breeze front, the western section of which is stopped in NURB. It is because, the urban heat island is isolated from (contiguous to) warm nocturnal sea in NURB (in SURB and HURB). CTRL shows earlier arrival of the land-breeze front, demonstrating the urbanization impact. In the wet case, HURB shows rainfall distribution as a combination of complementary distributions in NURB and SURB. Here, green spaces mediate transient negative feedback on rising daytime surface temperature by enhancing surface sensible heat flux, aiding to the local rainfall.