Quantifying atmospheric transport in the troposphere

There is substantial evidence for expansion of Hadley cell circulations and meridional shift of midlatitude circulations in a warming climate. The implications of these circulation changes for atmospheric transport have not been elucidated, especially as to the transport of chemical species or water vapor. Recent works have started to quantify atmospheric transport by isentropic mixing, diabatic circulation and the age of tropospheric air since last contact at the surface, analogous to our understanding of stratospheric transport. The goal of this study is to investigate the mechanisms responsible for tropospheric transport. We will use an idealized dry atmospheric dynamical core to simulate the age of tropospheric air from the tropical surface and from the midlatitude surface as compared with comprehensive GCMs and observations. The advecting flow will be further separated between the adiabatic flow and diabatic circulation. Furthermore, we will look into the effect of Hadley cell expansion and midlatitude circulation shift under climate change on tracer transport.