Characterization and Meteorological Drivers of Dust Events over California’s Central Valley

Dust events in California’s Central Valley pose severe risks to public health, regional air quality, and transportation. Yet, the climatology and meteorological drivers of dust events in the region are poorly characterized due to sparse monitoring and limitations of satellite observations. Using meteorological observations from 15 Automated Surface Observation System stations, we systematically catalog and analyze dust events across the Central Valley during 2005-2024, leveraging a hybrid approach that combines observer-reported dust codes with meteorological criteria that capture events missed by manual reporting, including those under cloudy and nighttime conditions. We identified 707 dust events, averaging ~35 dust events per year and increasing by 4.4 ±1.5% per year since 2005. These dust events are generally short-lived (≤1 h in ~78% of cases), occur mainly in the afternoon hours (14:00-18:00 local time), and are most frequent in the southern San Joaquin Valley between September and November. Self-organizing map analysis during the September-November peak dust season reveals four dominant synoptic-scale configurations driving dust events, characterized by anomalously strong surface winds, low relative humidity, and amplified mid-tropospheric troughs. Specifically, positively tilted troughs with northwesterly surface winds produced widespread dust events during abnormally dry to drought conditions, while negatively tilted troughs are associated with convective-driven fronts. Our results provide a robust foundation for improving dust forecasting and public health interventions in the agriculturally intensive Central Valley, experiencing intensifying drought and land-use pressures.