风应力桥梁作用下热带太平洋和热带大西洋相互作用的数值试验

Numerical experiments on interaction between tropical Pacific and tropical Atlantic through the windstress “bridge"

利用中等复杂程度热带大气和海洋模式研究了热带太平洋和大西洋SST通过风应力桥梁的相互作用.利用1958～1998年NCEP分析的海表面温度场(SST)强迫大气模式得到的表面风应力与NCEP分析的同期热通量共同驱动海洋模式,作为控制试验;和控制试验平行,但强迫大气模式的SST在某一海盆取为多年气候平均值的试验作为敏感性试验;比较控制试验与敏感性试验模拟,则可反映风应力桥梁作用下热带某海盆SST异常对其他海盆的影响.结果表明,热带某一海盆SST暖(冷)异常总是引起局地海盆表面西部西(东)风异常和东部东(西)风异常;热带太平洋SST暖(冷)异常导致的该海盆东部表面东(西)风异常可以扩展到热带大西洋,从而导致热带大西洋SST冷(暖)异常;热带大西洋SST暖(冷)异常导致的该海盆西部表面西(东)风异常可以扩展到热带太平洋,从而导致热带太平洋SST暖(冷)异常.

Interaction between the tropical Pacific and the tropical Atlantic through the wind stress bridge was numerically studied with intermediate models of global tropical atmosphere and ocean. In a control experiment, the atmospheric model was run from 1958 to 1998 with observed monthly SST data taken from NCEP reanalysis to generate surface wind stress, and with which the oceanic model was run over the same period with the heat flux taken and/or calculated from NCEP reanalysis data to generate SST. In a parallel experiment, everything is the same as in the control run except that the SST used to force the atmospheric model was fixed to climatological mean in a basin （the tropical Pacific or the tropical Atlantic）. The difference between the control and parallel experiments indicates how the SST anomaly （SSTA） in one basin influences the other through the wind stress bridge. The main results, are as follows. In general, the warm SSTA in one basin locally produces westerly anomaly in the west and easterly anomaly in the east, and vice versa. For a warm SSTA in the tropical Pacific, the surface easterly anomaly in the east of the basin extends into the tropical Atlantic, inducing a cold SSTA there, and vice versa. For a warm SSTA in the tropical Atlantic, the surface westerly anomaly in the west of the basin extends into tropical Pacific, inducing a warm SSTA there, and vice versa