摘要
厄尔尼诺-南方涛动(ENSO)春季预报障碍是ENSO预测的一个难点问题,弄清影响春季热带太平洋地区海表温度(SST)变化的动力和热力作用对于理解ENSO关键区SST的异常变化及ENSO春季预报障碍成因非常重要。本文利用BCC-CSM2-MR数值模式,模拟产生一套1986~2017年间相互协调的逐月海表风应力、感热、潜热、长波和短波净辐射能量、海洋流场等观测代用数据。利用这些数据对影响海温变化的动力和热力作用及其相对重要性进行了诊断分析,结果表明:(1)与其他季节相比,春季Ni?o3.4区海洋表层温度(后文中用T_S表示)呈现出独特的先增暖后趋冷的不对称季节性转换特征,这一变化主要是由于影响T_S的大气风应力、海流以及能量净通量在春季均表现出明显的季节性转换过程。进一步的分析表明,热力作用对局地海温的季节性变化影响最为重要,水平平流输送以反向作用为主,其中经向平流输送起到了反向作用,不利于该区域T_S的季节性转变,纬向平流输送仅在春季转为弱的正贡献,浅层垂直平流输送对春季T_S变化的影响很小。(2)动力热力作用与T_S异常的变化倾向相关关系也表明,春季Ni?o3.4区热力作用与T_S异常变化呈现显著的正相关,纬向海流异常的输送项也表现为正相关,而经向海流输送项展现出由负相关向正相关转化的特征。(3)对Ni?o3.4区T_S变化的方差贡献分析结果表明,春季热力作用对T_S的异常变化的贡献达50%以上,相关系数超0.7,其次是纬向、经向平流项贡献,各占10%~20%左右,但两者作用相反,其他项贡献较小。
The spring predictability barrier(SPB) of the El Ni?o–Southern Oscillation(ENSO) is a difficult problem in ENSO prediction. To understand how dynamic and thermal factors affect the variability of sea surface temperature(SST)over the tropical Pacific ocean during spring is very important in understanding SST changes in key areas and resolving the SPB problem. In this work, a set of monthly data, including sea surface wind stresses, sensible heat flux, latent heat flux, net longwave radiation, net shortwave radiation, and ocean current fields, coordinated with each other during1986–2017, were generated by BCC-CSM2-MR model simulation. Based on these data, we analyzed the dynamic and thermal influences and their contributions to the variability of SST(hereafter, T_S). The main results were as follows:(1) Compared with other seasons, in spring, T_S presented a unique asymmetric seasonal shift from warming to cooling in the Ni?o3.4 area. This was due to a similar shift in wind stress, net energy fluxes, and ocean current, which had a robust relationship with T_S. Further analyzes demonstrated that thermal effects play an important role in the variability of local T_S. In contrast, Horizontal advection is dominated by negative contribution. Meridional advection always showed a negative contribution to the seasonal variability of T_S. Meanwhile, zonal advection terms turned into a cooling effect from a warming effect on T_S during spring, and vertical advection effect was quite weak.(2) The interannual correlation between the tendency in T_S anomaly and dynamic/thermal effects showed that thermal heating, as well as zonal advection,were positively associated with the Ni?o3.4 T_S anomaly in spring. However, the correlation between meridional advection and the T_S anomaly changed from negative to positive during spring.(3) Quantitative analysis of the dynamic and thermal variance contributions in the Ni?o3.4 region also suggested that the contribution rate of thermal effect was >50%, and the corresponding correlation coefficient was >0.7. The contributions of zonal and meridional advection were about 10% and20%, respectively, but were inverse to each other. Other factors contributed less.
作者
赵鹤
颉卫华
吴统文
刘向文
ZHAO He;JIE Weihua;WU Tongwen;LIU Xiangwen(Chinese Academy of Meteorological Sciences,Beijing 100081;National Climate Center,Beijing 100081)
出处
《大气科学》
CSCD
北大核心
2020年第3期519-532,共14页
Chinese Journal of Atmospheric Sciences
基金
国家重点研究发展计划项目2016YFA0602100
国家自然科学基金项目41505094。
