The behavior of air parcel transport between hemispheres and between the troposphere and stratosphere is studied by directly calculating 180-day trajectories based on observed data. It is shown that air parcels from the extra-tropical troposphere of one hemisphere are transported to the other hemisphere through the upper troposphere. The estimated inter-heimispheric exchange time is about one year. The main pathway from the troposphere to the stratosphere is the tropical tropopause. The flow from the equatorial lower stratosphere branches off in two directions, i, e., one is the return flow to the troposphere through the sub-tropical tropopause gaps and the other is the poleward flow in the lower stratosphere.