| The NCEP/NCAR reanalysis data have been used to study the differences between theSomali jet and the cross-equatorial flow at 105°E in association with the Asian summer monsoonvariations. And we have also investigated interactions between the Northern and Southern Hemi-spheres in terms of cross-equatorial flows and some atmospheric oscillations (InterhemisphericOscillation, Arctic Oscillation and Antarctic Oscillation).The results are summarized as follows:(1) There are significant differences in periodicities as well as the time of climatic jumps ofthe interannual and interdecadal variations between two cross-equatorial flows. The Somali jet isclosely related to the subsystems including Indian summer monsoon, East Asian subtropicalsummer monsoon and South China Sea summer monsoon in the Asian summer monsoon regimes.However, the cross-equatorial flow at 105°E is closely related to the South China Sea summermonsoon variations. These two cross-equatorial flows are found to have different influences onthe circulation members of the Asian summer monsoon system.(2) The vertical distribution of global cross-equatorial flows shows that exchanges of the airmass and momentum between the Northern and Southern Hemisphere, which located at 925hPaand 150～200hPa, occurs in the Eastern Hemisphere in boreal summer and in the Western Hemis-phere in winter.(3) Air motions at the mid-high latitudes are relatively independent between the Northern andSouthern Hemispheres. Antarctic Oscillation is widely correlated to surface air pressure variationsin globe domain in boreal summer while to those in Antarctic regions in other seasons. Interhemi-spheric Oscillation is well correlated to surface air pressure in large areas and surface air temper-ature over northern Eurasia in spring, fall and winter. Therefore, both Antarctic Oscillation and thermodynamical forcings in the northern Eurasia continent are partly responsible for the Inter-hemispheric Oscillation, respectively.
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