Seasonal predictability of winter PM2.5 pollution severity in India through a strong pollution-extratropical storm connection.

India suffers from severe fine particulate matter (PM2.5) air pollution in winter that harms public health and disrupts economic activities. Seasonal prediction of pollution severity could facilitate proactive mitigation planning but is hindered by incomplete understanding of the drivers of pollution variations. Here, using over a decade of quality-controlled Indian government PM2.5 monitoring data, we find that ∼70% of the interannual variations in winter PM2.5 pollution across northern India are explained by western disturbances (WDs)-prevailing extratropical storms originating from the Mediterranean region-through PM2.5 removal via enhanced ventilation and precipitation. These WDs are regulated by the location and strength of the subtropical jet traceable to sea surface temperature (SST) anomalies across the North Atlantic and tropical Indian Ocean during the preceding autumn. Using these preseason SST anomalies, we demonstrate the potential to predict winter WD precipitation and PM2.5 pollution severity one season ahead, with good agreement with observations (r2 = 0.52 to 0.69), which could facilitate proactive public policies and stakeholder mitigation actions.