SEASONAL VARIATIONS OF THE TROPICAL INTRASEASONAL OSCILLATION AND ITS REPRODUCTION IN SAMIL-R42L9

Abstract:

Seasonal variations of the tropical intraseasonal oscillation (ISO) and relationship to seasonal variation of the climate background are studied by using NCEP/NCAR reanalysis data and output of SAMIL-R42L9. Analysis of NCEP data shows that spatial distribution of the tropical ISO has obvious seasonal variations, which are well consistent with the seasonal variation of climate background. The activity of the tropical ISO is, to a great extent, dependent on warm SST, strong convection, zonal western wind, strong precipitation and low-level moisture convergence. Main characteristics of the seasonal variations of the tropical ISO are captured by SAML-R42L9. Simulations of seasonal variation of climate background vary greatly with different variables. Results of SAMIL-R42L9 indicate that the seasonal variations of the tropical ISO in dynamical fields are more dependent on climate background than in heating fields and SAMIL-R42L9 cannot represent well the strong dependence of the ISO on the climate background present in NCEP/NCAR reanalysis data. It also suggests that seasonal variations of the ISO do not completely depend on that of climate background.