ENSO组合模态可预测性的季节-年代际变化

Seasonal-Decadal Variation in ENSO Combination Mode Predictability

厄尔尼诺-南方涛动组合模态(C-mode)是厄尔尼诺衰减期西北太平洋上空异常反气旋发展的主要驱动力,通常可以形成水汽输送通道,导致我国南部地区降水增多并发生严重的洪涝灾害,而在拉尼娜期间则情况相反。利用1981—2020年美国国家环境预报中心和美国国家大气研究中心再分析数据集的表面风场资料分析了C-mode可预测性的季节-年代际变化。结果表明:C-mode在2000年以后的可预测性明显下降,主要原因是其变率减小、强度减弱、信噪比降低等。在季节尺度上,C-mode存在“秋季预报障碍”,这与信号的季节循环密切关联,当C-mode在秋季进入衰退期时,信号强度最弱、变率最小,因此其秋季的可预测性降低。

Existing researches have suggested that the El Niño-Southern Oscillation(ENSO)combination mode(C-mode)is the main driver of anomalous anticyclone development over the northwest Pacific Ocean during El Niño decay,which usually creates water vapor transport channels leading to increased precipitation in the southern China,and vice versa during La Niña.This paper uses surface wind field data during 1981-2020 from the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis dataset,to analyze seasonal-decadal variation in the C-mode predictability.The results show that the predictability of C mode decreases significantly after 2000,and the main reasons for the decline of its predictability after 2000 include the decreasing variability,weakening intensity,and decreasing signal-to-noise ratio.On the seasonal scale,C-mode has an autumn predictability barrier,which is mainly related to the seasonal cycle of the signal,because when C-mode enters the recession period in autumn,its signal is the weakest and its variability is the smallest.