Understanding Urbanization’s Influence on Rainfall in Sydney Through High-Resolution Modeling and Storm Analysis

Urbanization alters land surface properties, impacting local and regional climates and increasing vulnerability to extreme weather events, such as heavy rainfall and heat waves. Understanding these effects requires high-resolution, long-term urban land use and land cover (LULC) data. To address this, we developed a scalable method that generates the first high-resolution, multi-year Local Climate Zone (LCZ) classification map for Greater Sydney (1990–2020) at five-year intervals. These maps reveal significant urban densification after 2005, with growth in mid- and high-rise LCZs and declines in open low-rise areas. We integrated these maps into the Weather Research and Forecasting (WRF) model by replacing a single dense urban category thereby enabling a more realistic representation of urban morphology (ranging from dense to sparse buildings across 1–10 categories) for long-term simulations. Next, to assess the impact of urbanization on Sydney's rainfall, sensitivity tests of extreme precipitation events were undertaken, comparing simulations using the default (USGS land cover) and LCZ land cover. These reveal significant differences in rainfall distribution both downwind and within urban areas. Additionally, daily mean surface temperature variations of around 1°C were found between the simulations. These results highlight the value of accurate land cover representation in capturing precipitation and temperature variations. Next, we are also employing weather radar-based storm object detection to examine how urban areas influence storm characteristics, including intensity, shape, and behaviour (e.g. merging, splitting). The findings will provide valuable insights into the complex relationship between urban growth and rainfall extremes.