全球变暖背景下气候内部变率导致热带辐合带移动的不确定性  

Uncertainty of the Intertropical Convergence Zone Shift Due to Internal Climate Variability in the Context of Global Warming

作　　者：肖展杰 郑小童 Xiao Zhanjie;Zheng Xiaotong(The Key Laboratory of Physical Oceanography,Ministry of Education,Ocean University of China,Qingdao 266100,China;College of Oceanic and Atmospheric Science,Ocean University of China,Qingdao 266100,China;Pilot National Laboratory for Marine Science and Technology(Qingdao),Qingdao 266237,China)

机构地区：[1]中国海洋大学物理海洋教育部重点实验室,山东青岛266100 [2]中国海洋大学海洋与大气学院,山东青岛266100 [3]青岛海洋科学与技术试点国家实验室,山东青岛266237

出　　处：《中国海洋大学学报（自然科学版）》2023年第9期27-39,共13页Periodical of Ocean University of China

基　　金：国家重点研究发展计划项目(2018YFA0605704);国家自然科学基金项目(41975092)资助。

摘　　要：基于两套模式的大集合试验结果,评估了气候内部自然变率对热带辐合带(ITCZ,Intertropical convergence zone)未来南北移动的影响。研究发现,模式间ITCZ的移动差异源自中高纬度的外强迫模拟差异,而气候内部变率主要通过热带过程调控ITCZ的位置变化。在通用地球系统模式大集合(Community Earth System Model Large Ensemble,CESM-LE)试验中,厄尔尼诺-南方涛动(El Nino-Southern Oscillation,ENSO)振幅变化的自然变率会通过中等和极端厄尔尼诺降水的非线性信号调制ITCZ的移动幅度,而在MPI-GE(the Max Planck Institute Great Ensemble)试验中,ITCZ的位置变化主要与大西洋海温梯度信号异常有关,相较而言ENSO振幅对ITCZ的影响很有限。总体而言,全球变暖背景下由于内部自然变率引起的ITCZ南北移动不确定性幅度能解释未来预估模式间的差异约为20%,但对ITCZ移动的模拟不确定性有贡献。Based on the energy-balance theory,the interhemispheric asymmetry of atmospheric energy meridionally shifts the tropical precipitation center,which is so-called the intertropical convergence zone(ITCZ).In a warmer climate,the ITCZ shifts northward due to asymmetric response between the northern and southern hemispheres,even though the anthropogenic GHG forcing is almost spatially uniform.However,there are still substantial uncertainty of ITCZ change among models,which are mainly due to the intermodel diversity in extratropical responses,such as aerosols.Besides the model response,climate internal variability is also an important source of uncertainty in model projections.This study evaluates the contribution of internal variability to the uncertainty in the ITCZ shift in future projections based on two sets of large ensemble experiment.It is found that internal variability influences the ITCZ shift mostly via tropical processes.In the Community Earth System Model Large Ensemble(CESM-LE),the uncertainty of ENSO(El Nino-Southern Oscillation)amplitude change can shift the ITCZ due to the nonlinear responses of precipitation to moderate and extreme El Nino events.However,in another large ensemble,the Max Planck Institute Great Ensemble(MPI-GE),the ITCZ shift is mainly related to the SST meridional gradient in the tropical Atlantic.By contrast,the modulation of ENSO’s amplitude can slightly impact the ITCZ due to its too strong cold tongue in the tropical Pacific.Overall,the internal variability-induced diversity in ITCZ shift can explain about 20%uncertainty among model projections,contributing to the uncertainty of ITCZ shift in climate models.However,its mechanisms are distinct to those from model spread.

关 键 词：全球变暖 热带辐合带经向移动 厄尔尼诺-南方涛动调控 未来预估 

分 类 号：P425.71[天文地球—大气科学及气象学]