北太平洋热带辐合带区上升运动的季节和年际变化特征

The Seasonal and Interannual Features of Ascending Motion Intensity and Position in the Intertropical Convergence Zone in the North Pacific

本文利用NCEP/NCAR再分析资料研究北太平洋热带辐合带区上升运动(ITCZω)强度和位置的垂直结构及其季节和年际变化。结果表明,气候平均态下西(东)ITCZω在高(低)层最强,低(高)层最弱,其位置随高度不变(偏北)。西ITCZω在8月最强,9月位置最北,2月最弱,位置最南;东ITCZω在8、9月最强,9月最北,2、3月最弱,位置最南,但中、高层的ω在11月也很弱。ITCZω强度最强(弱)的时间一般与位置的快速北跳(快速南撤)的时间相对应,并且有位置变化超前强度变化的表现。通过对ω气候值和异常值的经验正交函数分解,发现气候值EOF第一模态能很好的反映ITCZω的基本气候状态,具有准半年周期,第二模态反映了ITCZω的季节变化特征;异常值EOF第一模态空间场呈现东西反位相的特征,时间序列的功率谱分析最明显的周期为4.8 a。西ITCZω强度在厄尔尼诺年偏弱,拉尼娜年偏强;东ITCZω位置在厄尔尼诺年偏南,拉尼娜年位置则偏北。总体上ENSO事件对东ITCZω位置影响较大,而对西ITCZω强度影响较大。

The omega data and sea surface wind data from NCEP/NCAR reanalysis data during 1979 to 2007 were used to investigate the vertical distribution characters of ITCZω intensity and the position in the North Pacific and their seasonal and interannual features. The results show that in long-term average the strongest intensity of ITCZω in the Western （Eastern） Pacific is on the top （bottom） of troposphere and the weakest one is on the bottom （top）. The most northern position in the Western Pacific is almost the same as each other on three levels. In the eastern Pacific the most northern （southern） position is on the top （bottom）. The strongest intensity in the Western （Eastern） Pacific is in August （August and September） and the most northern position is in September. The weakest intensity and the most southern position are in February （February and March）. In the Eastern Pacific the intensity is also weaker in November. The time that ITCZω intensity reaches to the strongest （weakest） corresponds to the rapid northward （southward） shift of position. When the position is more （weaker）. And there are changes in position ahead of that northern （southern）, the intensity is stronger in intensity. By Empirical Orthogonal Function analyses（EOF）for climatic data and anomaly data, it is found that the first mode of climate data is the basic meteorological state of ascending motion with quasi-semiannual cycle and the second mode is the seasonal position fluctuation of ITCZω. The first mode of anomaly data is east-west dipole mode and in an 4. 8- year cycle by spectrum analysis of the time series. The intensity of ITCZω in the Western Pacific is weaker （stronger） in Elnino （Lanina） years. The position of ITCZω in the Eastern Pacific is more southern （northern） than normal years in Elnino （Lanina） years. In general, ENSO has great influence on the position in the Eastern Pacific and the intensity in the western Pacific.