Delhi, the capital city of India, has been witnessing polluted autumns and winters during the recent decade.
The post-harvest burning of paddy-crop residue in the neighboring states and the local emissions of pollutants,
with prevalent conducive meteorology, are responsible for the poor air quality in the capital city. Back in 2018-19,
the Indian Institute of Tropical Meteorology, under the guidance of the Ministry of Earth Sciences, India, led the
development of an 'Air Quality Early Warning System' (AQEWS) to alert the citizens and the policymakers about
the possible severe air-quality events about 7-10 days in advance. However, the policymakers need more precise
information on the potential sources responsible for the degraded air quality during a forecast severe air-quality
event. Such information would help them monitor and control such emission sources and thus assist them in making decisions
to manage air quality. Realizing this need, we have now extended the AQEWS with a 'Decision Support System' (DSS) for
air-quality management in Delhi.
DSS employs the state-of-the-science online chemistry transport model 'Weather Research and Forecasting with Chemistry' (WRF-Chem).
The modeling set-up utilizes the anthropogenic emissions inventory prepared by 'The Energy and Resources Institute' (TERI) for Delhi
and the surrounding 19 districts. The system assimilates
a) PM2.5 data from the 'Central Pollution Control Board' (CPCB) monitoring stations across the northern region of India, and
b) satellite retrieved aerosol optical depth from 'Moderate Resolution Imaging Spectroradiometer' (MODIS) instrument onboard
TERRA and AQUA satellites.
Moreover, DSS uses the Active Fire count data from the MODIS instrument to generate near-real-time fire emissions. This utility is
especially critical considering the agricultural burning activities occurring in the northern region of India post-monsoon. The DSS
runs with a horizontal grid spacing of 10 km and generates the forecasts and decision-support information for the
next 120 hours (i.e., five days).
DSS provides quantitative information about:
a) the contribution of emissions from Delhi and the surrounding 19 districts to the air quality in Delhi,
b) the contribution of emissions from 8 different emission sectors in Delhi to the air quality Delhi,
c) the contribution from biomass-burning activities in the neighboring states to the degradation of air quality in Delhi, and
d) the effects of possible emission source-level interventions on the forecast severe air-quality event in Delhi.
This information would explicitly highlight the most important emission
sources responsible for the degraded air quality in Delhi and suggest possible solutions to the policymakers. With a
plethora of quantitative data, the AQEWS integrated with DSS will be an essential tool for air-quality management in
Delhi and the surrounding region.