Numerical Simulations Of The Tropical Intraseasonal Oscillation

Simulation of the observed tropical Intraseasonal Oscillation (hereafter ISO) feature by atmospheric general circulation models (AGCMs) has been problematic in present. How to improve the ability of AGCM to simulate the tropical ISO is studied, meanwhile, assessment of the ability of AGCM to represent the oscillation is helpful for our further understanding its dynamics and may also help to improve the ability of AGCM. In this paper, the importance of the ISO in climate simulation is analyzed based on the root-mean square errors analysis on different GCM's results, firstly, and then, The sensitive of the simulated tropical ISO to cumulus paraterizations is studied using a single model with different cumulus schemes, and influences of diabatic heating profile are discussed ,especially. Other features of the tropical ISO, for instance, the Northward propagation of the ISO and its seasonality are also studied. Influences of changes in model resolution on the simulated oscillation are also studied in this paper. At last, impacts of convective momentum transport on the oscillation are assessed. Main results are summarized as followed:1. In terms of climate simulation using AGCM, simulation of Intraseasonal oscillation has important impact on the whole simulation. Root-mean square errors (RMSE) from the simulation of intrapersonal oscillation can take 30-40 percent of the total RMSE, meanwhile, the distributions of RMSE from simulated the intraseasonal oscillation are almost identical with the distribution of the total RMSE. This study further shows the significance of improving the ability of simulating the tropical ISO for climate simulation.2. Performance of AGCM in simulating the tropical ISO is highly sensitive to...