Impacts of deep convection on upper tropospheric composition diagnosed using chemical tracer measurements and CloudSat cloud data

This study investigates the impact of tropical deep convection on upper troposphere (UT) composition using in situ chemical tracer measurements from the `Convective Transport of Active Species in the Tropics (CONTRAST) Experiment' over the tropical western Pacific during the winter of 2014 and cloud observations from CloudSat. The UT enhancement of tracers emitted in the boundary layer is used to quantify the strength and height of maximum convective influence. The enhancement is found to have a compact relationship with tracers' photochemical lifetimes, especially in the layer between 10 to 12km where the CloudSat cloud fraction over the observation region maximizes (i.e., maximum outflow level). We hypothesize that deep convection plays an important role in shaping the tracers' vertical structure and the relative importance of convection depends on the tracers' lifetime. The Whole Atmosphere Community Climate Model (WACCM) was also utilized to compliment the in-situ measurements with idealized boundary layer tracers of different lifetimes. Together, the observed and modeled tracers allowed us to characterize the convective influence on the UT composition over the tropical western Pacific. We statistically compare the altitude of maximum convective enhancement determined using CloudSat data with tracer enhancement height based on CONTRAST observations and WACCM runs. Comparisons of observed and modeled convective influence on tracers' vertical distribution, the relation to lifetimes, and the level of maximum convective outflow are used to evaluate how convection is represented in models. Implications of these findings are discussed.