Utilisation of WRF-HYSPLIT modelling approach and GEMS to identify PM2.5 sources in Central Kalimantan – study case: 2023 forest fire

Biomass burning is a significant particulate matter (PM) source, substantially contributing to elevated PM2.5 levels. Exposure to PM2.5 has been associated with various severe chronic illnesses. Therefore, it is crucial to address biomass burning occurrences, mitigate their impacts, and manage their consequences effectively. A key strategy for managing biomass burning haze involves identifying its sources, which facilitates the implementation of fire prevention and suppression measures. This study explores the sources and impacts of PM2.5 emissions from forest fires in Central Kalimantan in October 2023 using an integrated approach. We employed the WRF-HYSPLIT (Weather Research and Forecasting model coupled with the Hybrid Single Particle Lagrangian Integrated Trajectory model) and satellite instruments, including the GEMS (Geostationary Environment Monitoring Spectrometer), MODIS (Moderate Resolution Imaging Spectroradiometer) and VIIRS (Visible Infrared Imaging Radiometer Suite), to identify PM2.5 sources and analyse their spatial distribution. Palangka Raya experienced substantial impacts from multiple hotspot occurrences on 4 October 2023, particularly from the south-eastern and eastern regions of Central Kalimantan and South Kalimantan. Conversely, Pangkalan Bun showed relatively lower PM2.5 concentrations on 2 October 2024 owing to prevailing sea winds. Most PM2.5 in Palangka Raya originated from the south-east. Geopotential height and topography analyses with wind plots suggested stable atmospheric conditions in Palangka Raya, whereas GEMS satellite data revealed high aerosol optical depth values, indicating elevated PM2.5 concentrations. These findings underscore the importance of understanding local meteorological conditions and hotspot distributions for effective management and mitigation of forest fire impacts on air quality in Central Kalimantan.