Decadal Variation of the Aleutian Low-Icelandic Low Seesaw Simulated by a Climate System Model(CAS-ESM-C)

Based on a simulation using a newly developed climate system model(Chinese Academy of Sciences-Earth System Model-Climate system component, CAS-ESM-C), the author investigated the Aleutian Low- Icelandic Low Seesaw(AIS) and its decadal variation. Results showed that the CAS-ESM-C can reasonably reproduce not only the spatial distribution of the climatology of sea level pressure(SLP) in winter, but also the AIS and its decadal variation. The period 496–535 of the integration by this model was divided into two sub-periods: 496–515(P1) and 516–535(P2) to further investigate the decadal weakening of the AIS. It was shown that this decadal variation of the AIS is mainly due to the phase transition of the Pacific Decadal Oscillation(PDO), from its positive phase to its negative phase. This transition of the PDO causes the sea surface temperature(SST) in the equatorial eastern(northern) Pacific to cool(warm), resulting in the decadal weakening of mid-latitude westerlies over the North Pacific and North Atlantic. This may be responsible for the weakening of the inverse relation between the Aleutian Low(AL) and the Icelandic Low(IL).

Two anomalous convective systems in the tropical western Pacific and their influences on the East Asian summer monsoon

根据经验正交函数(EOF)分解向外长波辐射资料,发现在热带西太平洋存在两个异常对流系统。除经典的菲律宾对流系统外(PC),在密克罗尼西亚群岛附近还存在另一个对流系统(MC)。MC是EOF分解的第一分量,解释的方差要大于PC。两个对流系统均受到热带海表温度异常的调制,其中PC与El Ni駉有关,而MC则与夏季中东太平洋海表温度异常有关。两个对流系统都能对东亚夏季风产生影响。一般而言,对流增强(减弱)时,西太平洋副高东退(西伸),强度减弱(增强)。PC减弱(增强)时,长江流域到日本的夏季风降水增加(减少)。与PC相比,MC对东亚大陆降水的影响较弱。此外,对流减弱的影响要大于对流增强的影响。

Simulation of the western North Pacific subtropical high in El Ni?o decaying summers by CMIP5 AGCMs

本文分析了耦合模式比较计划第五阶段(CMIP5)中的各大气环流模式对西北太平洋副热带高压系统在厄尔尼诺衰减期夏季的模拟。结果表明大部分模式都能够重现厄尔尼诺衰减期夏季的副高所伴随的大尺度环流的空间分布特征。大多数模式都可以合理地模拟出副高在厄尔尼诺衰减期夏季的位置相对于其气候平均态位置的向西偏移。这些模式对7至8月副高夏季季节内北跳的模拟强于对其东撤的模拟;几乎所有的模式都可以准确地模拟出副高的北跳,而只有三分之一的模式能够模拟出副高的东撤。模式中的副高在厄尔尼诺衰减期夏季位置的偏差很大程度上取决于其气候平均态位置的偏差。