Effect of National Clean Air Programme on radiative forcing over India

Abstract

Alarmingly high particulate matter (PM) levels are frequently blamed for India's poor air quality. As a result, the government has developed a few measures to regulate PM in the nation. For instance, the National Clean Air Plan (NCAP) was introduced in 2019 with the goal of bringing down PM concentrations in non-attainment cities (NAC) by 40% by 2026. This study endeavors to evaluate the accuracy of emission inventories in replicating the satellite observed AOD for the Indian region, and to identify the most suitable emission inventory among the available options for the common baseline year of 2015. Four databases (three global and one regional) that furnish emission estimates for air pollutants in India, which include EDGARv5, REASv3.2, ECLIPSE V6b and SMOGv1 were analysed.Simulations were conducted for different seasons using WRF-Chem V3.8.1. The key finding of the study is that SMOG emerged as the best performing emission inventory among all databases across all seasons, with an average Root Mean Square Error (RMSE) of 0.41 for the entire year. The simulations were performed with emissions projected for the years 2019 and 2026 from the best emission inventory obtained and fixing the Land use Land Cover (LULC) and meteorology. A decrease of 52.15 W/m2 in surface radiative forcing was observed across the Eastern India for the simulation period. This study provides valuable insights to India's regulatory bodies, highlighting the need to prioritize on source specific emission reduction to effectively combat the alarming increase in radiative imbalance which drives the climate change.