北太平洋海表温度及各贡献因子的变化

采用1958年1月至2007年12月SODA海洋上层温度的月平均资料,基于海温变化方程和统计分析方法,分析了北太平洋海表面温度(SST)异常特征及各局地因子贡献比例的变化。结果表明,伴随着1976/1977风场最强中心位置的南北移动,形成了两个北太平洋SST年际-年代际变化的异常中心:一个是位于30°N附近的副热带海盆内区,SST异常主要受风应力强度的主导;一个是位于40°N附近的副热带和副极地环流交汇区,SST异常主要受风应力旋度的位置即风场位置的影响。在副热带海盆内区,最强降温发生在1978-1982年,SST异常的主要局地贡献因子为海表热通量和经向平流,二者所占比例和约为50%~60%,均为同相增温或降温作用,余项所占比例约为20%~50%。在副热带和副极地环流交汇区,海盆内区和西部边界区的SST异常的跃变时间同为1975年,但是内区的垂直混合项的跃变时间早于西部5年左右。SST异常的主要贡献因子为海表热通量和经向平流,但在1983-1988年海温强降温期间,经向平流项贡献大于海表热通量项的贡献。两个区域的垂直混合项均为降温贡献,虽然量值小却显示出很强的年代际变化信号。平流项中经向平流最大,垂直平流最小。

Variation of sea surface temperature and its influence factors in the North Pacific

Based on the simple ocean data assimilation(SODA)1958-2007 monthly mean datasets and the thermal equation,the charateristics of interannual and interdecadal variability of the North Pacific sea surface temperature anomalies(SSTA)and their local factors are analyzed. The results show that,after Aleutian low deepened and moved southeastward around 1976/1977,the North Pacific SST cooled down in two regions: one is in the subtropical interior around 30°N,controlled by the wind stress anomalies;the other is located in the boundary region between the subpolar and the subtropical gyres around 40°N,controlled by the displacement of the zero wind stress curl line.In the subtropical interior region,the SST cooling reached its extreme during 1978-1982. Two main contributors are the surface heat flux and the meridional advection anomalies,which account for about 50%-60% of the SST anomalies. The residual term in the thermal equation accounts for about 20%-50% in this region. The SSTA shifted to negatives around 1975 almost simultaneously in the interior and western boundary region between the subpolar and the subtropical gyres. But the shift of vertical mixing term in the interior region occurred about 5 years earlier than in the western boundary region. Both the heatflux and the meridional advection terms are responsible for SST anomalies in this region,but the meridional advection terms dominant the SST variations during 1983-1988. The vertical mixing terms of these two regions are both small,but show strong decadal variations. The meridional advection is two times larger than the zonal advection.