东亚夏季风的强度与前期西太平洋暖池热含量异常的关系

Relationship between Intensity of East Asian Summer Monsoon and Preceding Heat Content Anomaly over Western Pacific Warm Pool

本文利用日本气象厅提供的历史海温资料、Hadley海温资料以及NCEP/NCAR再分析资料(1951~2010年)等探讨了东亚夏季风的强度与前期暖池热含量异常的关系。结果表明,西太平洋暖池热含量可以作为东亚夏季风强度的前期预测因子,两者正相关关系显著。本文选取相关系数更大、持续性更好的前期冬季暖池关键区(-5.5°~5.5°N;157.5°~170.5°E)热含量来进行预报。将暖池热含量指数和东亚夏季风指数均回归到夏季大气环流场上,发现在暖水年次年夏季西太副高偏弱、位置偏北,菲律宾以东以北洋面为气旋性环流,对流上升运动增强,赤道西太平洋地区为显著的西风距平,日本岛以东洋面为反气旋环流,对流下沉运动增强,日本岛以南、黄海至我国中东部地区为显著的东风距平,且前期2月西风带位置偏北,引起夏季海陆热力差异较大,最终导致东亚夏季风强度异常偏高;冷水年则相反。综上所述,当前期冬季西太平洋暖池热含量异常偏高(低)时,会造成次年东亚夏季风强度偏强(弱)。

Using the historical SST data provided by Japan Meteorological Agency and Hadley center, NCEP / NCAR reanalysis data (1951~2010), the relationship between the intensity of East Asian summer monsoon (EASM) and the preceding heat content anomalies over western Pacific warm pool and its possible reasons are studied. The results show that the intensity of EASM is positively related to the heat content anomalies over the warm pool. The 0~400 m heat content over the key area(-5.5°~5.5°N,157.5°~170.5°E)in preceding winter could be regarded as a good precursor of the intensity of EASM. In regressed field of atmospheric circulation against HCI and the intensity index of EASM, it is found that the western Pacific subtropical high (WPSH) is further north and much weaker. It shows strong rising motion located in the tropical monsoon trough region with greater westerly anomalies and strong sinking motion in the Meiyu front area with larger easterly anomalies. In the post February of the warm years, the position of westerly belt is further north, inducing much difference of thermal condition between sea and land in summer, which inclines to appear strong summer monsoon and vice versa. Above results indicate that the heat content anomalies are high (low) over the western Pacific warm pool in the preceding winter would cause the strong (weak) EASM.