Evaluating the role of city representation in modelling the urban precipitation effect of Kuala Lumpur

Abstract

Urbanization of Earth's land surface is one of the most impactful human interactions on the global ecosystem. Urban land cover substantially alters the transfer of heat, moisture, momentum, and aerosols between the surface and the atmosphere. These surface modifications are the first link in a complex process sequence that causes changes in clouds and precipitation, the so-called urban precipitation effect. Most studies on this topic to date have assumed a homogeneous representation of the city landscape, disregarding the potential effect of its heterogeneity on precipitation. We investigated the impact of Kuala Lumpur's urban precipitation effect through a set of sensitivity studies performed with the Weather Research and Forecasting model, in which different representations of the urban landscape were considered. We showed that including Kuala Lumpur city in the simulations causes a localised increase in accumulated rainfall, rainy day frequency and total extreme rainfall within the boundaries of the urban area. This effect is more pronounced when the city is represented as a homogeneous, high-density landscape compared to the more realistic heterogeneous case, where spatially varying urban canopy parameters are included in the model. Therefore, accurately representing urban areas in climate models is necessary to better estimate the urban precipitation effect.