Real-time air quality forecasting, part II: State of the science, current research needs, and future prospects

► A comprehensive review for real-time air quality forecasting (RT-AQF). ► Recent scientific advances of RT-AQF for potential model improvements. ► Review of major numerical & computational techniques to improve AQF skills. ► Detailed review of chemical data assimilation and ensemble forecasting techniques. ► Recommendations on major technical challenges and research priorities.