A253-08
Semi-direct effect of biomass burning emissions on downwind air quality over Northern India

Thursday, 17 December 2020: 05:58
Virtual
B Priyadharshini, Bennett University, Department of Civil Engineering, Greater Noida, India, Alaa Mhawish, Banaras Hindu University, Institute of Environment and Sustainable Development, Varanasi, India and Chandan Sarangi, Indian Institute of Technology, Madras, Department of Civil Engineering, Chennai, India
Recorded Presentation
Abstract:
In recent decades, agricultural biomass burning (BB) occurring during October-November months has been linked with degrading air quality and health over northwestern India (NWI), especially in Delhi. In this study, we used long-term data analysis (2007-2018) of a multi-satellite dataset to illustrate that the BB associated fire counts and corresponding aerosol loading have an increasing trend over NWI in the last decade. Specifically, Moderate Resolution Imaging Spectroradiometer (MODIS) fire count data exhibited an increase in the spatial extent of intense fires since the last decade over NWI. Further, aerosol optical depth (AOD) from Multi-Angle Implementation of Atmospheric Correction (MAIAC) at 550nm displayed an AOD trend higher by 50% in this region compared to the eastern parts of the Indo-Gangetic Plain (IGP). We also found that most of this enhancement is due to absorbing aerosols as the absorption AOD (AAOD) values from Ozone Monitoring Instrument (OMI) at 338nm are also increasing at ~5% rate in the last decade and is greater than 50% in NWI compared to eastern IGP. In addition, an analysis using the Central Pollution Control Board (CPCB) in situ PM2.5 measurements are performed to illustrate that PM2.5 values enhance by 30-40% under the influence of BB smoke. We used Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) to simulate a typical BB period in 2014. Results from these sensitivity simulations will also be discussed to explain a semi-direct effect pathway by which transported BB smoke plume can contribute to the enhancement in near-surface PM2.5 over downwind cities. The radiative effect of the absorbing aerosols decreases the planetary boundary layer height (PBLH) and thereby enhances the accumulation of locally emitted pollution near the surface. This semi-direct effect can potentially contribute to 50% of the total PM2.5 enhancement in downwind cities during the transported BB smoke influence period.
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