Department of Earth System Science

Convection in the tropics turns over the upper troposphere at rates (0.08 d⁻¹) comparable to photochemical processes controlling the absolute abundance of HO_x (OH + HO₂) and the abundance of NO_x (NO + NO₂) relative to HNO₃. Here we identify convection of boundary-layer CH₃OOH as a primary source of HO_x to the upper troposphere. Turnover of NO_x leads to NO/HNO₃ ratios much higher than predicted for local photochemical steady-state. Through convective transport the upper troposphere is more photochemically active in producing O₃, an important greenhouse gas.