赤道东太平洋海温正异常对西太平洋副高影响的数值模拟研究

simulating Influence of Positive Sea Surface Temperature Anomalies over the Eastern Equatorial Pacific on Subtropical High over the Western Pacific

利用ＬＡＳＧ九层大气环流谱模式及ＩＡＰ两层大气环流模式，模拟研究了不同持续时间的赤道东太平洋海表温度正异常（海表温度异常的持续时间分别为１月份，１～２月份，１～４月份及１～８月份，其他月份为气候ＳＳＴ）对西太平洋副高的影响。结果表明，尽管海表温度异常的持续时间不同，但其引起的西太平洋副高的异常演变及其分布却十分相似；同时，季风区的异常降水（进而异常潜热释放）随时间的演变及其分布也存在一定的相似性（对应于不同持续时间的赤道东太平洋的海表温度正异常，５月份印度洋至西太平洋地区都表现出赤道辐合带北移偏晚的特征）；季风区降水的这种变化同西太平副高的异常是一致的，从而揭示出这两种现象有可能存在着某种联系。结果还表明，导致这种大气响应场对赤道东太平洋海表温度异常持续时间不敏感的一个重要原因是大气内部过程的影响：中纬大气的内部Ｒｏｓｓｂｙ波源维持了热带地区激发的扰动在中高纬的存在，同时大气内部Ｒｏｓｓｂｙ波源对赤道太平洋地区的海表温度异常持续时间表现出不敏感性，正是由于这种不敏感性才导致了响应场对赤道太平洋地区海表温度异常持续时间的不敏感性。模拟结果还表明，在夏季赤道东太平洋存在海表温度正异常的情况，尽管大气内部动力过程?

IAP 2-level AGCM and LASG 9-level spectral AGCM are employed to simulate the effect of positive SSTAs with different duration (the SSTAs are prescribed only in January, January- February, January-April and January-August with the climatological SST in the other period respectively) over the eastern equatorial Pacific on the subtropical high over the western Pacific. The results suggest that despite the diversity of SSTAs duration, both the distribution and the temporal evolution of the anomalous subtropical high are similar, and so are the rainfall anomalies (therefore the latent release anomalies); the ITCZs are characterized by late northward displacement from the indian Ocean to the western Pacific in May. The agreement between the rainfall anomalies and the subtropical high anomalies over the western Pacific suggests the possible physical link between these two variables. The results also suggest that the atmospheric internal dynamical process is responsible for the insensitivity of atmospheric responses to the duration of SSTAs over the eastern equatorial Pacific. On one hand, the Rossby wave sources maintain the disturbances at middle-high latitudes which are excited in the tropics, on the other hand, the insensitivity of Rossby wave source to the duration of SSTAs over the eastern equatorial Pacific leads to the insensitivity of atmospheric responses to the duration of SSTAs over the eastern equatorial Pacific. The results show when the positive SSTAs are prescribed over the eastern equatorial Pacific, although the atmospheric internal dynamical process plays an important role, there is also obvious influence of positive SSTAs over the eastern equatorial Pacific in summer on the summer subtropical high over the western Pacific, therefore, the predictability of summer subtropical high over the western Pacific is determined by both the SSTA over the equatorial eastern Pacific and the atmospheric internal dynamical process. The different model results also suggest that the above results are model-independent.