青藏高原及东亚邻近区域对流层顶气压场的时空演变结构分析

利用经验正交函数分解(EOF)方法,对1948～2004年青藏高原及东亚邻近区域对流层顶气压场的时空演变结构进行了分析.由EOF分解得到的第1模态所占的方差贡献率较大,对应的空间分布场及其时间系数变化均能有效地反映气压场的主要演变特征.各季节不同模态呈现的高纬度、副热带和热带地区的空间场结构形态具有共性与季节性特征,且对流层顶断裂带位置变化也较为清晰.零等值线的季节性摆动,在冬季处于最北端.热带气压场随时间的变化与时间系数的变化相似性最大,不同模态的时间系数变化具有明显周期振荡现象.同时,对各季节第1模态的时间系数变化进行Morlet小波分析,进一步得到了不同季节气压场年际和年代际变化的结构特征.对流层顶冬半年的时域演变尺度大于夏半年,并具有复杂的多时间尺度结构.

STRUCTURE ANALYSIS OF THE SPATIAL-TEMPORAL FEATURE OF TROPOPAUSE PRESSURE FIELD OVER THE TIBETAN PLATEAU AND ADJACENT AREAS OF EAST ASIA

The spatial-temporal distribution feature of tropopause pressure field over the Tibetan Plateau and adjacent areas from 1948 to 2004 is analyzed using the method of Empirical Orthogonal Function(EOF).The spatial distributions and time coefficients of the first mode of EOF can effectively denote the main characteristics of the pressure field.The spatial structures in different seasons of different modes of EOF show common characteristics in the high latitude,subtropical and tropical area,and the variations of the location of tropopause break are relatively clear.The zero isolines are at the northernmost in the winter.The change of the tropical pressure field is most similar with that of the time coefficients,and the time coefficients of different modes present obvious characteristics of periodical oscillation.In addition,the Morlet wavelet method is used to analyze the change of time coefficients of the first mode in each season,and the interannual and interdecadal characteristics of pressure field structure in different seasons are obtained.At the tropopause the period of time in winter is larger than that in summer,and it has complicated multi-time scale structure.