初夏南亚高压中心经向位置年际变化的一个关键预测信号

基于欧洲中期天气预报中心的ERA-interim再分析资料，应用统计和动力诊断方法，分析了初夏南亚高压（SAH）中心位置年际变化规律及其与青藏高原东南部热源异常的联系.结果显示：初夏SAH中心位置具有显著的准6 a变化特征，但仅有其经向位置与初春青藏高原东南部（SETP）大气潜热活动存在显著的负相关关系；与偏强的初春SETP潜热活动相联系，异常的西风出现在青藏高原的南侧20°N附近，偏西风异常北侧的正涡度异常及其南侧的负涡度异常，加强了青藏高原附近的异常气旋以及印度次大陆半岛及印度洋上空的异常反气旋，这一异常环流形势可以从初春一直维持到初夏，不利于SAH向北移动，最终导致初夏SAH中心位置偏南；反之，初春SETP异常偏弱的潜热活动将以大致相反的物理过程，最终使得初夏SAH中心位置偏北.冬末春初的SETP潜热活动是预报初夏SAH中心经向位置年际变化的一个关键信号.

A key predictor for the interannual variability of South Asian High core's meridional position in early summer

In this paper, the interannual variability of the South Asian High (SAH) core position in early summer and its relationship with the anomalous diabatic heating over Southeastern Tibetan Plateau (SETP) were analyzed using European Centre for Medium Range Weather Forecasts (ERA-interim) reanalysis data and methods of statistical and dynamic diagnoses. The results showed that the SAH core position in early summer significantly varies on the quasi-six-year band. Only the interannual variability of its meridional position significantly correlates negatively with the activities of latent heating over the SETP. Associated with the stronger latent heating over the SETP in early spring, the westerly anomalies appear around the south flank of the Tibet Plateau near 20°N. The positive vorticity anomalies on the north side and the negative vorticity anomalies on south side of the westerly anomalies strengthen the anomalous cyclones near the Tibet Plateau and the anomalous anticyclones over the Indian Subcontinent Peninsular as well as the Indian Ocean. This configuration of the anomalous atmospheric circulations, lasting from early spring to early summer, is not beneficial to the northward movement of the SAH, and finally further causes the SAH′s core position to be farther southward than normal. Associated with the weaker latent heating, the opposite phenomena occur, resulting in the SAH’s core position being farther northward than normal. Therefore, it can be said that the early spring latent heating over the SETP is a key predictor for the interannual variability of the meridional SAH’s core position in early summer.