Mechanisms of convection-induced modulation of passive tracer interhemispheric transport interannual variability

Interannual variations of tropical convection impact atmospheric circulation and influence year-to-year variations of the transport of trace constituents in the troposphere. This study examines how two modes of convective variability, anomalous intensification and meridional displacement of centers of tropical convection, impact interhemispheric transport (IHT) interannual variability. Two modeling frameworks are employed, an atmospheric general circulation model (AGCM) and a chemical transport model (CTM) forced with a realistic, interannually varying circulation field, to investigate the zonally averaged and regional-scale influences of the modes of convective variability on passive tracer IHT. Both convective modes are found to modulate IHT interannual variability. While convective displacement appears to be the more quantitatively significant mode within the AGCM framework, anomalous convective intensity and displacement are of equal importance in the CTM framework. The results suggest that the modeling of atmospheric tracer transport interannual variability requires accurate representation of multiple aspects of convective variability.