Abstract: In this paper, the global normal sea-level pressure fields have been exa mined by means of harmonic analyses. It is shown that the dimensions and distributions of the oceans and continents are responsible for the difference in circulations between the two hemispheres. The effect of continents that is oaring with the latitudes much more pronounced in low latitudes in summer while in high latitudes in winter. The well-known role of Eurasia and African in the formation of monsoons over Easten Asia is comfirmed.