CMIP5多模式对阿留申低压气候特征的模拟检验与预估

利用观测的海温资料和海平面气压资料,检验了CMIP5(Coupled Model Intercomparison Project 5,CMIP5)多模式对阿留申低压(Aleutian Low,AL)特征指数的时空分布和变化的模拟能力;从AL周期及变化趋势等方面,分析了CMIP5模式预估的未来AL的变化特征。结果表明,CMIP5模式及其集合平均能够很好地模拟AL的环流结构,对AL的气候态有着较强的模拟能力,尤其是模式对于东太平洋海表温度的模拟能力直接影响其对于AL的模拟效果。模式的集合平均对变率强度的模拟偏强,且对于变率的模拟效果逊于对气候态的模拟。22个模式中的16个模式能模拟出AL强度指数的年代际变化周期,对年代际周期有着较好的刻画能力。Historical试验下对于AL的变化趋势存在着较大的不确定性,而相对于两种不同排放情景,随着排放的增加,AL更加偏北,强度增强,年际、年代际周期变得更加显著。在两种排放情景下模式的集合平均以及多数模式模拟出AL有着向北和增强的趋势。

Evaluation and Projection of the Climatic Characteristics of Aleutian Low Based on CMIP5 Models

The observed sea surface temperature, sea level pressure and multi-model simulations of the Coupled Model Inter-comparison Project 5 (CMIP5) are explored to analyze the temporal and spatial variation of the Aleutian Low (AL) index in the North Pacific. Furthermore, the decadal cycle variability is evaluated and the long-term trend is estimated based on simulations of the CMIP5. Results show that the CMIP5 multi-model simulations can well reproduce the climatology and variability of the AL circulation. Specifically, the simulated AL is sensitive to simulated sea surface temperature in the East Pacific. However, the comparison of the CMIP5 multi-model ensemble results and observations indicates that the intensity of the standard deviation of the ensemble mean is stronger than that of the observation, while the model ability for standard deviation simulation is worse than that for mean climate state simulation. Also, 16 out of the 22 CMIP5 models can reproduce the decadal oscillation cycle of the AL. In the Historical experiment, there is a large disagreement over the long-term trend of AL among the model results. It is suggested that the AL strengthens and extends northward under two typical Representation Concentration Pathway scenarios (i.e. RCP4.5 and RCP8.5), particularly under the RCP8.5 scenario. More significant annual and inter-decadal variations are found under the RCP8.5 scenario. It is also noted that the ensemble mean and most of the models can forecast the AL intensity and its northward extension. However, the reason for the eastward extension of AL is still controversial.