The Tropical Atmospheric Conveyor Belt: A Coupled Eulerian-Lagrangian Analysis of the Large-Scale Tropical Circulation

The Hadley circulation is a key element of the climate system. It is traditionally defined as the zonally averaged meridional circulation in the tropics, therefore treated as a zonally symmetric phenomenon. However, differences in temperature between land and sea cause zonal asymmetries on Earth, dramatically affecting the circulation. This longitudinal dependence of the meridional circulation evokes questions about where and when the actual large-scale tropical circulation occurs. Here, we look into the connection between the longitudinally dependent meridional circulation, and the actual large-scale transport of air in the tropics using a coupled Eulerian and Lagrangian approach. Decomposing the velocity field into rotational and divergent components, we identify how each component affects the actual circulation. We propose an alternative definition for the circulation, which describes the actual path of air parcels in the tropics, as a tropical atmospheric conveyor belt.