风应力桥梁作用下热带太平洋和热带印度洋相互作用的数值试验

利用中等复杂程度全球热带大气和热带海洋模式的数值试验,模拟分析了热带太平洋和热带印度洋通过风应力桥梁的相互作用过程.利用NCEP再分析的1958～1998年SST强迫大气模式得到的风应力与NCEP再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的SST变率,揭示了热带某海盆SST异常通过风应力桥梁作用对其他海盆SST的影响及其过程.数值试验结果表明:热带某海盆SST暖(冷)异常一般总是引起该海盆上空西部西(东)风异常和东部东(西)风异常;热带太平洋SST暖(冷)异常导致年际尺度上印度洋上空东(西)风异常和年代际尺度上热带印度洋风场辐散(合),该风应力导致热带印度洋年际SST暖(冷)异常以及年代际SST冷(暖)异常,但这种异常均较弱;热带印度洋SST暖(冷)异常导致热带太平洋上空东(西)风异常,该风应力异常在年际和年代际尺度上均导致热带太平洋SST冷(暖)异常,但年代际尺度上异常更明显.考虑到热带印度洋SSTA受热带太平洋SSTA影响大,并且热带太平洋SST暖(冷)异常主要通过表面热通量导致热带印度洋SST变暖(冷)的观测事实,文中揭示的热带印度洋SST暖(冷)异常通过风应力桥梁作用导致热带太平洋SST冷(暖)异常的结果表明,热带印度洋SSTA对于热带太平洋SSTA主要起着一种负反馈作用,并且这种负反馈作用在年代际尺度上更为明显.

Numerical experiments on interaction between the tropical Pacific and the Indian Ocean through the wind-stress "bridge"

Intermediate tropical atmospheric and oceanic models were used to study the interaction between the tropical Pacific and the Indian Ocean through the wind-stress "bridge".In the control run,the observed SST for 1958~1998 was used to force the atmospheric model generating the surface wind-stress,which was then used to force the oceanic model with the surface heat flux taken from NCEP reanalysis to reproduce the SST.Two parallel sensitivity runs are the same as the control run except for the SST used to force the atmospheric model which was prescribed with climatology in the tropical Pacific and in the tropical Indian Ocean,respectively.The difference between the control and sensitivity runs indicates effect of the SST anomaly(SSTA) in a specific oceanic basin on the other basin through the wind-stress bridge.Such numerical experiments suggest the following results.A positive(negative) SST A in a basin generally produces a westerly(easterly) anomaly in the west and an easterly(westerly) anomaly in the east of the basin.A positive SST A in the tropical Pacific induces an easterly anomaly in the tropical Indian Ocean,which results in a weak positive interannual SST A and a weak negative interdecadal SST A in the tropical Indian Ocean;and vice versa.A positive SST A in the tropical Indian Ocean induces an easterly anomaly in the tropical Pacific Ocean,which results in a negative SST A on both the inter annual and interdecadal times cales in the tropical Pacific,and viceversa.Considering the observational fact that the SSTA in the tropical Indian Ocean is more influenced by the tropical Pacific and that the SSTA with the same polarity in the former basin always follows the latter basin,the results suggest a negative feedback role of the tropical Indian Ocean in the tropical Pacific SSTA,which is more obvious on the interdecadal times cale.