季节内振荡对热带印度洋 SST 日变化的调制--一维混合层模式的诊断结果

摘要

热带印度洋 SST 的日变化幅度受到大气季节内振荡（Madden-Julian Oscillation，MJO）的调制，其在 MJO 对流最强（弱）位相达到极小（大）值，并且在 MJO 对流增强位相显著强于其对流减弱位相。本文利用逐时的再分析海表通量强迫一维海洋混合层模式，定量地诊断了 MJO 事件中 SST 日变化的差异成因。结果表明，SST 日变化在 MJO 对流最强与最弱位相的显著差异主要是由短波辐射的季节内变化所致（40％），其次是风应力（38％）和潜热通量（14％），其他要素的影响较小。而 SST 日变化在MJO 对流增强与减弱位相所呈现的不对称特征，主要是由纬向风应力的不对称性所致，这是 MJO 扰动结构与背景环流相互作用的结果。%Modulated by the Madden-Julian Oscillation (MJO),the diurnal range of sea surface temperature (SST) peaks on the convection suppressed phase and drops to its lowest on the convection active phase.What’s more,this kind of diurnal range on the developing phase of MJO is much larger than that on the decaying phase.Using a one-dimensional ocean mixed layer model,forced by the newly developed hourly reanalysis of sea surface fluxes,the cause of the difference of diurnal range of SST during the evolution of MJO is diagnosed quantitatively.It is dem-onstrated that the intro-seasonal variation of sea surface shortwave radiation is the main reason for the striking difference of diurnal range of SST between suppressed phase and active phase of MJO (40%).The intra-seasonal variation of wind stress (38%)and latent heat flux (14%)are also important.Due to the scale interaction between MJO perturbation and background circulation,the asymmetry of zonal wind stress determines the asymmetry of di-urnal range of SST between developing and decaying phase of MJO.