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利用NCEP/NCAR再分析资料,对1948/1949-1999/2000共52个冬季的北太平洋上空中纬度阻塞异常的气候特征进行了统计分析,小波分析和功率谱分析结果表明该区域阻塞发生的频数具有很明显的3-7年的年际振荡和年代际变化特征。同时2-7年带通平均的小波方差谱分析结果表明阻塞的这种年际变化的振幅存在着缓慢下降的趋势,且气候突变在20世纪70年代,这进一步证明了北太平洋上空的阻塞活动具有年代际变化特征。对强阻塞异常的冬季和弱阻塞异常的冬季分别进行合成分析,结果表明,对于阻塞异常强的冬季,北太平洋500 hPa高度异常场表现为典型的 PNA型的波列,风暴路径则在 40°-50°N之间从日界线以西向东北方向加强并分裂成两个中心,而SST异常在中纬度太平洋则对应着典型的PDO型,在赤道地区则为类La Nina型的海温分布。而对于阻塞异常弱的冬季则对应截然不同甚至相反的分布特征,即500 hPa高度异常场表现为符号相反的PNA型,风暴路径中心在日界线附近呈纬向型分布,同时SST异常在赤道地区则为典型的El Nino型的海温分布。以上结果揭示出北太平洋阻塞活动的年际变化可能主要与热带海温的遥响应相联系,而年代际变化则主要与中纬度局地的PDO型海温及其通过斜压瞬变波的海-气相互作用有关。
Based on the NCEP / NCAR reanalysis data, the climatic characteristics of the 1948 / 1949-1999 / 2000 winter over the North Pacific over mid-latitude clogging anomaly were statistically analyzed. The results of wavelet analysis and power spectrum analysis showed that the frequency of occlusion occurred in this area There is a clear 3-7 year interannual oscillation and decadal variability. At the same time, the band-to-band variance analysis of bandpass averaged 2-7 years showed that the amplitude of this interannual change of clogging showed a slowly decreasing trend and the abrupt change of climate occurred in the 1970s, which further proved the obstruction activity over the North Pacific With decadal variations. The results show that the anomalous 500 hPa anomaly field in the North Pacific shows a typical PNA-type wave train and the storm path is at 40 ° for the winter with extremely strong anomalies and the winter with weak anomalies. -50 ° N from the west to the northeast, and the SST anomalies correspond to typical PDO types in the middle latitudes and the La Nina-type sea temperature distributions in the equatorial regions. For winter with abnormally weakened anomalies, they correspond to distinct or even opposite distributions. That is, the anomalous 500 hPa anomalies exhibit the opposite sign of PNA type. The center of the storm path is zonal distributed near the daily boundary and the anomaly of SST in the equatorial region It is a typical El Nino-type SST distribution. The above results reveal that the interannual variation of the blocking activity in the North Pacific may be mainly related to the teleconnection of the tropical SST, while the interdecadal variations are mainly attributed to the PDO-type SST at midlatitude and the sea through the baroclinic transient wave - Gas interactions.