Convective Transport of Tropical Marine Boundary Layer Species into the Upper Troposphere and Relation to Species Lifetime: In Situ Measurements and Global Model Simulation

This study investigates the influence of tropical deep convection on distribution of trace gasses in the tropical upper troposphere (UT) using data from the Convective Transport of Active Species in the Tropics (CONTRAST) Experiment conducted over the tropical western Pacific during January and February of 2014. Fifty-five chemical species measured during the CONTRAST campaign are analyzed with lifetimes ranging from less than a day to several years. The vertical profiles of these species suggest that they fall into three main groups delineated by their lifetime: 1) very long-lived trace gases demonstrating a nearly constant vertical structure, 2) intermediate lifetime species exhibiting a reverse s-shape with distinct UT enhancement, and 3) extremely short-lived gases showing sharp decrease with height and only sporadic occurrences of UT enhancement. The ratio of UT to boundary-layer (BL) concentration is used as a simple metric to characterize the efficiency of convective transport. The UT-BL ratios are found to have a compact relationship with tracers’ photochemical lifetimes. In addition to observed data, we also examine simulations from the Whole Atmosphere Community Climate Model (WACCM) with artificial tracers with lifetimes similar to our observed trace gasses. The Community Atmosphere Model with chemistry (CAMchem) is also used. Modeled results fit well with results from measured trace gasses indicating that their cumulus parameterization schemes are working reasonably well. Determining efficiency of convective transport for tracers of varying lifetimes is crucial for understanding not only the dynamics of these deep convective systems, but also the chemical impacts on the UT