利用1980-2010年共31个冬季的GODAS 海洋同化资料,以5~366 m 次表层海温构造西太平洋暖池区域的热含量,分析了冬季西太平洋暖池次表层热含量的时空特征、持续性以及对其邻近区域的气候异常影响,结果表明:(1)整体一致性分布是冬季西太暖池区次表层热含量年际变化的主导模态,其时间系数的年际振荡较好地代表了暖池区次表层热状况的年际异常。暖池区热含量的变化与ENSO 事件联系密切,它能保持超前两季以上的显著自相关,持续性较赤道中东太平洋海温异常更为稳定。(2)冬季暖池区热含量异常对后期春、夏季暖池热状况产生持续影响,相应的暖水体积变化导致暖水的经向输送及垂直交换,对后期春夏两季暖池及邻近区域尤其是菲律宾海的表层海温、海表热通量变化有较大影响。(3)冬季暖池区热含量上升对应春季菲律宾海以东洋面OLR 数值下降以及降水偏多,所引起的对流活动加热异常导致热带及副热带西北太平洋位势等压面抬升,进而对西太副高产生影响。之后,此区域相应的海表热通量交换加强,对流层低层形成强大的异常气旋,海气相互作用加强,加上对流加热异常,使得冬季暖池热含量异常与夏季副热带高压变化联系更加紧密。因此冬季暖池区热含量可作为春、夏季西太副高变化和西北太平洋夏季风强度的有效预测因子。
英文摘要:
Based on the GODAS oceanic assimilation data, this paper studies the spatial-temporal characteristics and persistency of the winter sub-layer heat content (HC) over the Western Pacific warm pool (WP) and its impacts on the anomalies of circulation, convective activity and the subtropical high. The results are shown as follows. (1) The dominant EOF mode of HC anomalies over warm regions displays uniform anomalies over the WP, with two maximum centers near 6 °N and 6 °S. Its corresponding time coefficient (PC1) shows significant relationship with the WP anomalies of sea level height and warm water volume. We further construct a heat content index (HCI) by using tropical WP regional mean HC, which is highly consistent with the annual fluctuation of PC1 and thereby well represents the anomalous sub-layer heat condition over WP. The HCI also correlates well with SST indices in the Nino3.4 region (Nino3.4). However, the persistency of HCI is better than the Nino3.4. It shows significant auto-correlation up to 9~10 months ahead without the "spring-barrier" compared to the Nino3.4. (2) The persistent positive anomalous HC results in the change in warm water volume and exchange of meridional and vertical oceanic water over WP, leading to anomalously warm upper-level sea temperature and positive upward heat flux in the subsequent spring and summer. (3) The positive HC anomalies connect with negative OLR anomalous values and positive precipitation anomalies in the subsequent springtime east of the Philippine Sea, which gives rise to enhanced convective activity, latent heat release and upper-layer uplifting. Then the associated summer surface heat flux is intensified and a strong anticyclone shows up east of the Philippine Sea. Meanwhile, the convective heating anomalies still persist in this region. These results lead to close connection between the winter HC anomalies and the corresponding subsequent Western Pacific subtropical high anomalies in the spring and this relationship becomes intensified in the following summer. Therefore, the winter sub-layer HC anomalies in WP can be an effective factor for forecasting the intensity of Western Pacific subtropical high and even the Western Pacific monsoon in the subsequent spring and summer.