CMIP6模式对北太平洋中纬度海洋锋强度与冬季风暴轴关系的模拟及预估

Simulation and projection of the relationship between the North Pacific mid-latitude oceanic frontal intensity and the wintertime storm track based on the CMIP6 model

本文利用参与第六次国际耦合模式比较计划(CMIP6)的高分辨率气候模式CNRM-CM6-1-HR资料,对北太平洋中纬度海洋锋强度与冬季风暴轴的关系开展模拟和预估。研究发现,该模式能够较好地再现海洋锋强度与风暴轴的正相关关系,即当海洋锋加强(减弱)时,风暴轴在其主体及下游区域显著增强(削弱),但模拟的正相关关系在风暴轴北部强于观测,这是由于模拟的海洋锋强度与低层大气斜压性的正相关关系在其北部偏强。对比模式在历史试验和未来4种共享社会经济路径(SSPs)下的模拟结果发现,全球变暖背景下,海洋锋强度与风暴轴依然存在显著的正相关关系,但在风暴轴气候态大值区及其北部区域呈现减弱趋势,正相关关系减弱程度在高辐射强迫情景(SSP5-8.5)下最大,在中等至高辐射强迫情景(SSP3-7.0)下最小。进一步研究发现,未来海洋锋强度与低层大气斜压性的正相关关系呈现出类似的减弱趋势,说明未来海洋锋与风暴轴关系的变化主要取决于海洋锋与低层大气斜压性关系的变化。

In this study,the relationship between the North Pacific mid-latitude oceanic frontal intensity and the wintertime storm track was simulated and projected based on a CMIP6 high-resolution climate model CNRM-CM6-1-HR.Results show that the model well reproduces the positive correlation between the oceanic frontal intensity and the storm track.The storm track activity is intensified(weakened) in its climatological peak and downstream as the oceanic front strengthens(weakens).However,the simulated positive correlation is stronger than the observation in the storm track northern region,which is mainly attributed to the greater positive correlation between the oceanic frontal intensity and the near-surface baroclinicity.By comparing the relationship between the oceanic frontal intensity and the storm track under four different Shared Socioeconomic Pathways(SSPs) with the historical run,it is found that there tends to exist the significant positive correlation under global warming,while the correlation will weaken in the storm track climatology and northern region,with the largest reduction in the high radiation scenario(SSP5-8.5) and the least reduction in the medium to high radiation scenario(SSP3-7.0).Further analysis indicates that the positive correlation between the oceanic frontal intensity and the near-surface baroclinicity also exhibits a similar weakened trend,which suggests that the projected changes in the relationship between the oceanic front and the storm track are mainly determined by the future changes in the relationship between the oceanic front and the near-surface baroclinicity.