NO_x-Induced Changes in Upper Tropospheric O₃ During the Asian Summer Monsoon in Present-Day and Future Climate

The upper tropospheric ozone (O-3) strongly influences the atmosphere's radiative budget. Using the Aerosol and Chemistry Model Intercomparison Project simulations, we study the influence of present-day and future anthropogenic nitrogen oxides (NOx) emissions on the upper tropospheric O-3 concentrations over India during the Asian summer monsoon (ASM). We observe that the upper tropospheric O-3 concentrations increased 1.5 times over the ASM anticyclone region during the ASM due to higher NOx emissions in 2014 compared to 1850, and their transport due to convection. These NOx-induced O-3 changes exert a regional positive radiative forcing of 0.6 Wm(-2) at the top of the atmosphere. The upper tropospheric O-3 increases in the future with increasing NOx emissions. However, air quality policies to reduce surface NOx emissions also reduce the upper tropospheric O-3 over India during the ASM.