Performance of high resolution (400 m) PM2.5 forecast over Delhi
Chinmay Jena, Sachin D. Ghude, Rajesh Kumar, Sreyashi Debnath, Gaurav Govardhan, Vijay Kumar Soni, Santosh H. Kulkarni, Gufran Beig, Ravi S. Nanjundiah, M. Rajeevan
Abstract
Abstract 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.