Abstract: The atmosphere circulation variability is one of the fundamental problems in the researches on the tropical Indian Ocean Dipole (IOD) mode event. The authors analyze the variability of the wind vorticity field and divergence field during IOD event based on the observation and the numerical model. The result indicates that both the divergent and rotational parts of the wind field present the first order baroclinic pattern in the vertical direction and symmetric pattern in the horizontal direction respectively. In the lower atmosphere, the rotational part shows a pair of symmetric anticyclones around the equator during the positive phase of IOD event and the divergent part shows the divergence in the eastern Indian Ocean and the convergence in the western Indian Ocean. Both the divergent part and the rotational part could generate zonal easterly wind above the equator region in the tropical Indian Ocean, which supports the air－sea positive feedback mechanism. The upper circulation is just reversed with the lower one.