CHENNAI: An IIT Madras-led international study has found that accounting for atmospheric air pollution could improve the simulation of extreme rainfall and urban flooding. The findings were published in Natural Hazards and Earth System Sciences, a peer-reviewed, open-access international journal covering research on natural hazards.
The study found that explicitly accounting for atmospheric aerosols (tiny particles suspended in the air that influence cloud formation and rainfall) can improve the simulation of intense rainfall and subsequent flood inundation.
Researchers from IIT Madras, GFZ Helmholtz Centre for Geosciences in Germany, the Japan Aerospace Exploration Agency (JAXA), and Kathmandu University studied Chennai’s extreme rainfall and flooding event of December 2015.
Using the Weather Research and Forecasting (WRF) model, the researchers simulated the atmospheric processes associated with the event under different aerosol conditions. They incorporated cloud condensation nuclei (CCN), around which cloud droplets form, to examine how atmospheric aerosol conditions influence rainfall.
The resulting rainfall data were then coupled with HEC-HMS for hydrological modellling and HEC-RAS for flood-inundation modeling in the Adyar basin. The study found that explicitly representing aerosols produced an approximately 22% improvement in simulated rainfall over the Adyar basin compared with the control simulation. This improvement was carried through the modelling chain, resulting in an approximately 50% improvement in the accuracy of simulated flood inundation.
Chandan Sarangi, department of Civil Engineering, IIT Madras, and corresponding author, said rainfall’s spatial and temporal distribution is often not adequately captured by weather models. Representing aerosol-cloud interactions, he said, could help better capture extreme rainfall patterns over urban areas and consequently improve flood simulations.
Professor, S N Kuiry of IIT Madras said more accurate rainfall forecasts could also support critical water-resources decisions, including reservoir storage and release during extreme rainfall events.
The researchers cautioned that the framework is not yet an operational flood-forecasting system. Further studies across other extreme rainfall events and cities, along with improved high-resolution observations of aerosols and urban emissions, are required to validate the approach.