Land Use and Land Cover (LULC) play a crucial role in the regional climate models, as they influence various physical processes interconnected with energy, mass, and atmospheric interactions. This study has examined the impact of high-resolution LULC data on the accuracy of the Weather Research and Forecasting (WRF) model with the Urban Canopy Model in capturing the thermal environment of the Colombo Metropolitan Region (CMR) during heatwaves (HWs). In the performed simulations we used four LULC datasets: USGS, MODIS30, MODIS15, and Esri (Sentinel2). Our investigation is the first application of the WRF model to study the thermal environment in a tropical city such as Colombo. This is also the first research investigation of HWs in the Sri Lanka context from the mesoscale viewpoint. Additionally, this is the first time high-resolution Esri land-use data have been used in a numerical model to examine the thermal environment. By evaluating the three HW cases, we compared the simulation outcomes with observational data from three meteorological stations in CMR. The results from numerical simulations revealed that the LU4 dataset provided the closest agreement with observed Land Surface Temperatures (LST). Daytime LSTs in urban areas peaked above 45 °C, while nighttime temperatures reached 30 °C in commercial zones. Coastal regions consistently exhibited lower temperatures, with daytime LSTs ranging from 40 to 45 °C and nighttime LSTs from 25 to 30 °C, compared to the urban cores. LU4 showed the closest alignment with Himawari satellite data, ensuring superior accuracy. Temperature anomaly analysis indicated that LU4 reduced daytime temperature anomalies by up to 2.5 °C and nighttime anomalies by 1.0 °C compared to other datasets. Statistical evaluations (R = 0.94 in Colombo) further highlight the importance of high-resolution LULC data for enhancing the accuracy of the WRF model in representing urban thermal environments.
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