Long-term variability in biogenic emission fluxes and ozone over South Asia: Integrating remote-sensing observations with modeling

The Indian subcontinent is a large geographical system which experiences diverse natural and anthropogenic processes influencing the regional air quality, atmospheric chemistry and climate. However, ground-based observations are often sparse and limited to a few chemical species and the models have larger uncertainties in simulating aforementioned processes for Indian conditions. In this regard, we combined the potentials of remote sensing data and modeling to study the long-term variations in natural emissions and surface ozone. While the mean ozone levels are higher over the northern India, the long-term trend is seen to be more pronounced ( 0.4 ppbv y-1) over the central-east regions in the vicinity of higher biogenic emissions of isoprene. In addition, tropospheric column ozone shows increasing trends over the northern Indian Ocean and surrounding larger regions including Southeast Asia. We find widespread enhancement in ozone across South Asia and stronger biogenic emissions over peninsular India during the warmest year (2016) as compared to the climatological mean distributions. Our study suggests the need to conduct comprehensive in-situ observations of biogenic volatile organic compounds for formulation of effective policies to mitigate the impacts of global warming on the air quality over South Asia.