太平洋区域季内振荡的一种负反馈过程

利用1981—2002年美国国家气象中心（National Meteorological Center,NMC）逐日海表温度（sea surface temperature,SST）、10 m高处风场（V）及逐月混合层厚度（mixed layer depth,mld）资料,研究了太平洋区域海表温度季内振荡的气候及异常特征,重点探讨了北太平洋区域海表温度季内振荡的维持机制。研究发现,太平洋区域海表温度存在3个季内振荡强度气候高值区,即热带东太平洋（终年存在）、西北太平洋（北半球春、夏、秋存在）、西南太平洋（南半球夏季前后存在）,它们出现在气候混合层厚度最小的区域和季节。海表温度季内振荡强度年际异常与混合层厚度年际异常存在显著负相关,在物理上,这种关系比它与海表温度异常的关系更直接。北太平洋区域5—9月地面风场与海表温度季节内振荡的基本耦合模态揭示出以漂流和感热输送为动力的一个负反馈过程,它存在于薄混合层海区,这是该海区强海表温度季内振荡的维持机制。

A Negative Feedback of the Intraseasonal Oscillation in the Pacific Ocean

The climatorological and anomalous features of the intraseasonal oscillation （ISO） in the Pacific domain have been investigated using the NMC（National Meteorological Center） sea surface temperature （ SST）, winds at 10 m and monthly mixed layer depth （mld） from 1981 through to 2002. Three centers of strong ISO in the SST are detected in the Pacific. The center of SST ISO in the eastern equatorial Pacific can be detected in all the year, however, the other two centers in the northwest and the southwest Pacific respectively are season-dependent. In the summer hemisphere, the intensity of ISO seems much stronger than that in the winter hemisphere. These three strong ISO regions are closely related to the variations of the oceanic mld. The thinner the mld, the more active the ISO. This suggests that the ISO in the Pacific involves the ocean dynamical processes. On the other hand,the SVD1 mode of the SST and the winds at 10 m above the ocean surface shows that the ISO is coupled with the surface air motion through a negative feedback between the atmosphere and the Ocean, and exists in the sea area where the told is thinner. Which explains the existence of SST intraseasonal oscillation in the North Pacific.