Abstract: In this paper, the spatial and temporal variations of cross-equatorial currents around the globe are shown and discussed firstly by the pressure-longitude vertical cross-sections and then by the time-longitude cross-sect ions at 850 mb and 200 mb level respectively. In lower layer of atmosphere over the eastern Hemisphere there exist 5 passages of southerly cross-equatorial currents during the summer months, which become northerly during the winter months, exhibiting annual variation of monsoon nature- But over the western Hemisphere there are 3 passages of southerly currents and 2 passages of northerly currents. They all do not change in direction for the whole year. And then the coherent circulation systems are elucidated-It is demonstrated that the establishment and maintenance of Somali Jet appear to be preceded by a certain precur -sory variations of the subtropical high and westerlies over Australia and West pacific. There may be a definite temporal sequence of processes in seasonal variation of the atmospheric circulation systems over different parts of the globe.