黑潮及其延伸区海表温度变化特征与大气环流相关性的初步分析

Preliminary analyses on characteristics of sea surface temperatures in Kuroshio and its extension and relations to atmospheric circulations

为了研究黑潮海表温度的时间变化特征,以预测黑潮海表温度变化趋势,本文利用哈德莱中心1941—2009年海表温度资料定义了一个黑潮温度指数KI,来表征吐噶喇海峡以东黑潮及其延伸区的海温变化.由小波分析得到,KI具有准3、7年的年际振荡特征和准20年的年代际变化特征,此外KI还具有明显的季节锁相特征.KI与太平洋年代际振荡(PDO)及厄尔尼诺-南方涛动(ENSO)有很好的滞后相关性.通过美国国家环境预报中心/大气研究中心再分析资料合成分析发现KI为正异常时,赤道东太平洋海温异常变暖(即厄尔尼诺发生),哈德莱环流加强,使得西风动量的输送增强,造成阿留申低压加深(PDO为暖相),进而冷却黑潮延伸区的海表温度并使黑潮延伸区向东延伸,这一"ENSO-PDO-黑潮海温变化"的过程具有滞后性,从而使得ENSO指数、PDO指数可以作为黑潮温度变化的前兆因子,对于预测黑潮海温变化及周边气候均具有一定的意义.

A sea surface temperature （SST） based index, denoted as KI, is designed to characterize the holistic feature of Kuroshio east of the Tokara-kaikyo and its extension on the purpose of predict its SST trend. The KI is calculated on the base of the Hadley Center＇s monthly SSTs during the period 1941-2009. The wavelet analysis showed that the KI displays inter-annual and inter-decadal oscillations, dominated by quasi-triennial, quasi 7-yr and 20-yr time scales. In addition, the KI is shown to be phase-locking to seasonal cycles. It is found that there are significant temporally-lag correlations between the KI and the Pacific decadal oscillation （PDO） index as well as between the KI and the ENSO index. A set of composition analyses using the NCEP/NCAR reanalyses indicate that when the KI shows a positive anomaly, the SST becomes abnormally warm in the equatorial eastern. Pacific, the Hadley circulation is intensified, and consequently the transportation of the westerly momentum is enhanced. The enhanced Hadley circulation and transportation of the westerly momentum give rise to the deepened Aleutian low pressure, then cool the Kuroshio extension and the north Pacific basin and cause the KE extend east. The above ＂ENSO-PDO-Kuroshio＂ process need some response time, that is to say, we can forecast the SST variation on the Kuroshio on the basis of the ENSO and PDO, which is very significant to predict the climate in China.