副热带南北太平洋经向模与ENSO的关系

RELATIONSHIP BETWEEN THE SUBTROPICAL SOUTH/NORTH PACIFIC MERIDIONAL MODES AND ENSO

本文利用Hadley中心的海表面温度、海洋再分析资料ORAS4(Ocean Reanalysis System 4)的海表面高度、NCEP(National Centers for Environmental Prediction)的海气界面风场及热通量等数据,分析了1948-2018年期间副热带南、北太平洋经向模(South Pacific meridional mode,SPMM、North Pacific meridional mode,NPMM)的基本特征及其与厄尔尼诺-南方涛动(El Niño and Southern Oscillation,ENSO)的关系。结果显示,两个副热带太平洋经向模对应的海表面温度异常都呈现南北反位相的偶极子结构,并与ENSO关系密切:当Niño3.4滞后北太平洋经向模10个月时,二者达到最大正相关;Niño3.4滞后南太平洋经向模6个月时,二者达到最大正相关。换句话说,在副热带太平洋发生北太平洋经向模正位相事件(北太平洋东南暖,西北冷)1 a后或者南太平洋经向模正位相事件(南太平洋东北暖,西南冷)半年后,热带太平洋可能会发生厄尔尼诺事件。据此,利用二元线性回归方法建立了基于南太平洋经向模和北太平洋经向模预测ENSO的统计模型,得到拟合的Niño3.4和观测的Niño3.4之间的相关系数达0.57,预测效果良好。

The relationship of the subtropical South/North Pacific Meridional Modes(SPMM,NPMM)with ENSO was investigated using sea surface temperature(SST)data from Hadley center,Sea surface height(SSH)from ORAS4(Ocean Reanalysis System 4),and wind and air-sea heat flux from NCEP-NCAR reanalysis 1(1948—2018).Results show that the SSTA associated with the two meridional modes both show north-south dipole patterns and are closely related to ENSO.The significant maximum positive correlation appears when Niño3.4 lags NPMM for 10 months,there are significant maximum positive correlations when Niño3.4 lags for 6 months,with the peak correlation appearing at 6-month lag.In other words,about one year after a positive NPMM(North Pacific:warm in the southeast and cold in the northwest)appears in the north Pacific,or half a year after a positive SPMM(South Pacific:warm in the northeast and cold in the southwest)happens in the south Pacific,and there will be an El Niño event in the tropical Pacific.A binary linear regression model was constructed based on SPMM and NPMM to improve ENSO prediction.The correlation between the reconstructed Niño3.4 and the observed Niño3.4 reached 0.57.