On the evaluation of different WRF urban canopy schemes for the study of precipitation related to urban heat island in Kuala Lumpur

Cities can have a significant impact on local microclimate. Higher temperatures that often characterise urban fabric can influence other meteorological parameters, such as precipitation. In this study, we investigated how the urban heat island (UHI) of Kuala Lumpur impacts rainfall through a set of sensitivity studies performed with the Weather Research and Forecasting (WRF) model. Many studies have already pointed out that the UHI can increase local rainfall, but they disregarded the city heterogeneity to large extent. Here, we investigated the effect of the city on precipitation incorporating different representations of the urban landscape. We performed three simulations with different urban land cover: 1) without city (control experiment) 2) with the urban terrain represented homogeneously and 3) with the urban land represented heterogeneously with the surface classification in the 11 categories of the Local Climate Zone (LCZ) system. We observed that the consideration of the city of Kuala Lumpur in the simulations results in a localised increase in mean annual precipitation and mean intense precipitation within the boundaries of the urban area. However, in the case of the homogeneous representation of the city, the increase is more pronounced than in the case of the heterogeneously represented city. In the former case, the increases also occur over a larger area and the impacts propagate more strongly into the upper layers of the atmosphere. Thus, a more realistic representation of the city and its heterogeneities limits the urban-induced effects on precipitation.