THE INTRASEASONAL OSCILLATION AND ITS INTERANNUAL VARIABILITY—A SIMULATION STUDY^*

The atmospheric intraseasonal oscillation(ISO)and its interannual variability are simulated by the atmospheric general circulation model,which was developed at the Institute of Atmospheric Physics.Two numerical experiments were performed,corresponding to the AMIP-I and AMIP-II simulations,respectively.The model reasonably reproduces the major aspects of the intraseasonal oscillation,including the propagating property and the seasonal differences in the tropics,the wavenumber structure of ISO in the globe,and the global coincidence in the interannual variation of ISO.Comparison of the results between the two experiments suggests that improvement of the boundary forcing or considering the air-sea interaction may help to improve the simulation on the ISO and its interannual variability.