中文摘要：

根据对大气原始方程的定性理论和相空间的理论研究,初始场对数值模拟的作用会随着时间的增长而逐步衰减。文章分析初始场作用衰减理论的关键问题,通过对大气环流谱模式SAMIL和ECHAM的数值试验,在实际的计算环境中研究其初始场作用的变化情况。研究中使用到对舍入误差干扰的一种集合消减方法（REME）,保证了验证试验所受舍入误差的影响小于给定的范围。结果表明有舍入误差存在的计算环境中,当初始差别较大时,其逐步衰减到一个波动值。而对于特别微小的初始场差别,其长期影响也应是衰减的,但由于计算精度有限,可能会出现增大到一个波动值的现象,这些结果与非线性误差理论所描述的误差饱和现象一致。试验得到了具体模式的衰减速率曲线,发现衰减需要的时间范围大约为40—60d。文中还利用初始场作用衰减的理论探讨了如何解释初始场集合预报（IME）能够减少模拟结果误差的现象。

英文摘要：

The complete dynamical equations of the atmospheric motion and the qualitative theory of nonlinear atmosphere with dissipation and external forcing in Hilbert space suggest that the initial condition will not affect the status of a long-time numerical simula- tion with AGCMs. In this research, we first introduce the key points for understanding the decay of initial condition effect, and then employ two atmospheric general circulation models （AGCM）, SAMIL and ECHAM, to investigate the effect of initial condition on the simulation results in an actual computing environment with round off errors. The round-off error mean ensemble （REME） experiments are conducted to reduce the uncertainty caused by round-off errors. The results indicate that in the actual computing environment, a big initial condition error/spread will lead to a small fluctuating final error. But for a tiny initial condition error/spread, it will lead to the same-magnitude final fluctuating error. This is against the theoretical analysis. However, the discrepancy can be explained by the existence of the round-off errors which are not considered in the theoretical analysis. The final error balance is consistent with the error saturation property indicated by the nonlinear error growth theory. The initial error decay curves of SAMIL and ECHAM are obtained, from which we find that the initial condition error in the two AGCMs decays to the final error within about 40 - 60 days of integration. At last, we used the initial error decay theory to conclude that the initial mean ensemble （IME） is capable of reducing the error in climate simulation studies.