Performance of high resolution (400 m) PM(2.5) forecast over Delhi

This study reports a very high-resolution (400 m grid-spacing) operational air quality forecasting system developed to alert residents of Delhi and the National Capital Region (NCR) about forthcoming acute air pollution episodes. Such a high-resolution system has been developed for the first time and is evaluated during October 2019-February 2020. The system assimilates near real-time aerosol observations from in situ and space-borne platform in the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) to produce a 72-h forecast daily in a dynamical downscaling framework. The assimilation of aerosol optical depth and surface PM(2.5) observations improves the initial condition for surface PM(2.5) by about 45 µg/m(3) (about 50%).The accuracy of the forecast degrades slightly with lead time as mean bias increase from + 2.5 µg/m(3) on the first day to − 17 µg/m(3) on the third day of forecast. Our forecast is found to be very skillful both for PM(2.5) concentration and unhealthy/ very unhealthy air quality index categories, and has been helping the decision-makers in Delhi make informed decisions.