Atmospheric transport of ozone between Southern and Eastern Asia

This study describes the effect of pollution transport between East Asia and South Asia on tropospheric ozone (O-3) using model results from the Task Force on Hemispheric Transport of Air Pollution (TF HTAP). Ensemble mean O-3 concentrations are evaluated against satellite-data and ground observations of surface O-3 at four stations in India. Although modeled surface O-3 concentrations are 1020 ppb higher than those observed, the relative magnitude of the seasonal cycle of O-3 is reproduced well. Using 20% reductions in regional anthropogenic emissions, we quantify the seasonal variations in pollution transport between East Asia and South Asia. While there is only a difference of 0.05 to 0.1 ppb in the magnitudes of the regional contributions from one region to the other, O-3 from East Asian sources affects the most densely populated parts of South Asia while Southern Asian sources only partly affect the populated parts of East Asia. We show that emission changes over East Asia between 2000 and 2010 had a larger impact on populated parts of South Asia than vice versa. This study will help inform future decisions on emission control policy over these regions. (C) 2015 Elsevier B.V. All rights reserved.