The Feature Changes Of Tropical Atmospheric Interseasonal Oscillation Under The Background Of Global Climate Warming. And Numerical Simulation

The possible changes of intraseasonal oscillation (ISO) feature in tropical atmosphere under the background of global climate warming by means of both diagnosis and numerical simulation are explored in this article. First, some main features possible changes of ISO in tropical atmosphere under the background of global climate warming, such as ISO intensity, central place of ISO chief active region, season change, and propagation feature, have been diagnosed using the last NCAR/NCEP reanalysis data about six year. It is found that the place of ISO main active region remain no change but their intensity and range increase and enlarge to a certain extend, and these changes have difference in season .There is a reductive tendency in season difference when global climate become warmer. The ISO intensity in tropical atmosphere totally appear a heightening tendency. The change of climate background also affect the propagation feature of ISO in tropical atmosphere. In general, the eastward-propagation ISO energy relatively increase but the westward-propagation ISO energy relatively weaken when the climate become warmer. There is also the difference in the period range of ISO under the different climate background. During the stage of relative stable, the ISO energy is relative small but the range of ISO main period is relatively concentrative (in 30～60 days). During the stage of relative warming, the ISO energy is relative large but the range of ISO main period is relatively scatter (in 20～100 days).Second, the possible changes of ISO feature in tropical atmosphere under the situation of simulative natural variability and anthropogenic impact are explored, using the long-range integration results both the control test which the CO₂ density maintain no change as the quantity before industrial revolution and the double test which the CO₂ density increase by 1% every year from 280ppm (the density before industrial revolution) to 560ppm. These results are simulated by a coupled GCM-- FGOALS1.0_g, which is developed in the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric physics(LASG), Institute of Atmospheric physics(IAP). It is showed that the conclusion that the ISO intensity increase ,the main active region range enlarge and ISO season difference reduce may be the the interdecadal variation of atmosphere intraseasonal oscillation system itself but not the cause that the climate become warmer because of CO₂ density increase in atmosphere. Under the state of simulative natural variability, the tropical eastward-propagation or westward-propagation ISO energy ratio on the whole maintain a equilibrium state, But the tropical eastward-propagation or westward-propagation ISO energy ratio appear a slow increasing tendency when thinking of anthropogenic impact, this is consistent with the conclusion diagnosed by means of the last NCAR/NCEP reanalysis data about six year, the last NCAR/NCEP reanalysis data about six year. So the conclusion that ISO energy of eastward/westward-propagation relatively increase/reduce my be caused by the CO₂ density increasing. Finally, the relation among the feature change of ISO in tropical atmosphere, ocean SST and tropical atmosphere circulation system are analyzed preliminarily. It is showed that the SSTdipole in Indian ocean affect the atmosphere ISO in main active region greater than the Nino3 SST.