大气模式中季节内振荡特征对不同海温强迫场的响应

Responses of Madden-Julian Oscillation in Community Climate Model to Different Sea Surface Temperature Forcings

利用美国国家大气研究中心 (NCAR)的全球大气模式 (CCM3) ,分别以月平均和周平均海表温度 (SST)为强迫场进行 2个积分试验 (称为 CCMM和 CCMW试验 )。积分结果与观测资料的对比分析发现 ,CCM3模拟大气季节内振荡 (MJO)信号的强度均较观测资料偏弱 ,而其中以CCMW模拟的强度略大而较接近真实。表明 SST强迫场包含更真实的季节内变化信息对提高模拟 MJO强度有作用。 CCMM与 CCMW模拟 MJO活动的时间位相均与观测差别较大 ,直接原因在于 CCM3中降水季节内振荡与 SST变化的相关关系不正确 ,而更根本的问题在于大气模式无法反映资料分析发现的季节内时间尺度的 SST与大气的相互作用。

Daily mean output from two realizations to the last version of National Center for Atmospheric Research(NCAR) Community Climate Model (CCM3), forced by different sea surface temperatures (SSTs), are analyzed in the present study with the aim to discover the response of the tropical intraseasonal oscillation(Madden-Julian Oscillation; MJO) to the intraseasonal variability of SST forcing. The results indicate that variabilities on the seasonal-interannual time scale show good agreement in the two integrations, while the simulated MJOs exhibit remarkable difference in both intensity and phase. Based on the tropical zonal, mean zonal wind at 200 hPa, MJO in the weekly SST forced integration has more realistic intensity, seasonality and interannual variability than the one forced by monthly SST although the simulated MJOs are overall weaker comparing with the reanalysis data. In the tropical ocean, the intraseasonal variability of precipitation shows noticeable difference between the two integrations. The one forced by the weekly SST has a better intraseasonal adjustment to the seasonal precipitation. The correlation between tropical SST and precipitation is more significant in the weekly SST forced integration than that in the other.