Abstract This study applies a simple two‐box model to quantify the convective transport of trace gas species in the tropics. The model characterizes the interplay between convective transport and chemical reactions using two parameters: convective turnover time and the species' chemical lifetime. Using airborne measurements of 42 trace gases from the CONvective Transport of Active Species in the Tropics field campaign, we show that this model reproduces over 90% of the observed variability ( R 2 > 0.9) in the observed ratio of upper troposphere (UT) to boundary layer mixing ratio—the UT fraction—across the 42 species, with the UT fraction serving as an indicator of convective venting efficiency. A key insight is that this efficiency is well captured by the ratio of chemical lifetime to turnover time. The turnover times derived from the box model are consistent with the mean transit time from the Transit Time Distribution framework of earlier studies. This physically intuitive box model provides an observation‐based diagnostic for evaluating convective transport in global chemistry‐climate models and for improving our understanding of chemistry‐climate interactions.
Wang et al. (Fri,) studied this question.