Enhancing Air Quality Decision-Making Activity in Indian Subcontinent By Integrating Multi-Scale Modeling with Earth Observations

Protecting public health from exposure to air pollution that exceeds India’s National Ambient Air Quality Standards (NAAQS) has emerged as a top priority for the Government of India (GOI). For timely alerting the public of upcoming air pollution episodes and implementing temporary emission control measures to reduce the magnitude of predicted air pollution events, the National Science Foundation National Center for Atmospheric Research (NSF NCAR) in collaboration with the Indian Institute of Tropical Meteorology (IITM) and the Indian Meteorological Department (IMD) have developed an air quality early warning systems (AQEWS) for entire India at 10 km grid spacing. The system currently assimilates the Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD) retrievals to improve initialization of aerosol chemical composition but we are transitioning to the assimilation of Visible Infrared Imaging Spectroradiometer (VIIRS) AOD retrievals to ensure AQEWS continues to benefit from space-borne observations of AOD after MODIS reaches the end of its lifetime. For the period of 10 Oct to 20 Nov 2017, we find that that VIIRS AOD assimilation provides similar benefits as MODIS AOD does with improvements in the accuracy of fine particulate matter forecasts in Delhi. However, the impact of VIIRS AOD assimilation is not as large as it is from MODIS AOD because of larger errors in VIIRS AOD retrievals and smaller geographical coverage compared to that of combined Terra and Aqua. MODIS AOD assimilation also led to large improvement in particulate matter forecasts during a dust event that affected western India. The Indian AQEWS has also been extended to four other megacities namely Jaipur, Mumbai, Pune, and Ahmedabad. These forecasts are disseminated to the public via https://ews.tropmet.res.in. We have also developed a decision support to help policy makers from the Commission for Air Quality Management (CAQM) make informed decisions about temporary emission controls to reduce the amount of predicted pollution in New Delhi. The CAQM imposes and/or lifts-off temporary restrictions on targeted emission sources to improve air quality particularly in Delhi. These capabilities of the AQEWS will be discussed in detail during the presentation.