Abstract: The climatological structure and characteristics are studied using the 17-year NMC monthly winds and OLR data. It is found that the tropical circulation consists of zonal Walker Cells and meridional Hadley Cells. They are directly driven by the thermal difference in the tropics. The wind directions in upper troposphere and in low level are often opposite. There is a close relationship between the mean flow and the perturbation field. The maximum perturbation kinetic energy is linked with the westerly basic flow and the minimum perturbation kinetic energy is linked with the easterly. There are also strong divergence fields in the tropics and they are closely related to the convective activities in tropics.