CMIP6模式大气中南北半球际涛动的季节循环

利用1958—2014年47个CMIP6模式输出资料和NCEP/NCAR再分析资料,研究了模式大气中南北涛动(InterHemispheric Oscillation,IHO)的季节变化特征,且评估了CMIP6对IHO季节特征的模拟能力。结果表明:47个CMIP6模式都能模拟出IHO的季节演变特征,但模式间存在一定差异。通过比较,筛选出模拟IHO季节循环较好的16个模式,它们能成功模拟出半球大气质量的时间演变和空间结构。进一步分析表明,水汽对IHO季节变化有抵消作用且半球内部水汽质量变化可驱动越赤道质量流的产生;地表净短波辐射夏高冬低,其加热造成的水汽蒸发在水汽质量变化中起到重要作用;地表净长波辐射在春秋变化幅度较大,与大气质量逐月变化吻合。对比再分析资料表明,CMIP6模式模拟的半球大气质量的峰谷值变化有明显的月份偏差,且CMIP6模式模拟的地表气压异常值的偏差主要出现在北太平洋、欧亚大陆、南半球中纬度地区和两极极区,模拟的南北半球的蒸发和降水量、赤道风场、地表净长波和短波辐射通量等均存在明显的偏差。

Seasonal cycle of interhemispheric oscillation in atmosphere of CMIP6 models

Using the output data of 47 CMIP6 models and the NCEP/NCAR reanalysis data from 1958 to 2014,this paper studies seasonal variation characteristics of interhemispheric oscillation (IHO) in the model atmosphere,and evaluates the ability of CMIP6 to simulate the seasonal characteristics of IHO.Results show that all 47 CMIP6 models can simulate the seasonal evolution characteristics of IHO,but there are some differences among the models.Through comparison,16 better models for simulating the seasonal cycle of IHO are selected,which can successfully simulate the temporal evolution and spatial structure of hemispheric atmospheric mass.Further analysis shows that water vapor can counteract the seasonal variation of IHO,and the change of water vapor mass in the hemispheres can drive the generation of cross-equatorial mass flow.The surface net short wave radiation is higher in summer and lower in winter,and the water vapor evaporation caused by its heating plays an important role in the change of water vapor mass.The surface net long wave radiation changes greatly in spring and autumn,which is consistent with the monthly change of atmospheric mass.Compared with the reanalysis data,it shows that the peak valley variations of hemispheric atmospheric mass simulated by CMIP6 models have obvious monthly deviations,and the deviations of surface pressure anomalies simulated by CMIP6 models mainly occur in the North Pacific,Eurasia,mid-latitude regions of the Southern Hemisphere and polar areas.There are obvious deviations in the simulated evaporation and precipitation,equatorial wind field,surface net long wave and short wave radiation fluxes in the Northern and Southern Hemispheres.