Hadley环流与北太平洋涛动的显著关系

利用NCEP/NCAR月平均再分析资料，分析了冬季（11～4月）Hadley环流与北太平洋涛动（NPO）的变化特征以及它们之间的关系.本文选取0°~30°N区域里最大质量流函数来描述北半球Hadley环流强度随时间的演变，利用(20°N, 180°~160°W) 和 (60°N, 180°~160°W) 区域平均的标准化海平面气压差代表NPO强度.结果表明，冬季北半球Hadley环流与NPO的变化形势非常一致，两者都具有显著的年际和年代际变化（70年代前处于负位相，80年代之后处于正位相），同时还呈现出明显的增强趋势.Hadley环流变化与NPO异常的关系非常密切，在年际和年代际时间尺度上都具有显著的正相关.这种强相关性在大气环流场上可以得到很好的印证.研究还揭示，太平洋地区10°~30°N下沉支和40°~60°N上升支的异常运动可能是这种关系存在的主要内在原因.

Significant relationship between Hadley circulation and North Pacific Oscillation

The present study addresses the variability of Northern Hemispheric Hadley circulation and North Pacific Oscillation (NPO) in winter and their relationship, employing NCEP/NCAR data for the period 1954~2003. In this research, the index for Hadley circulation intensity is defined as the maximum positive value of the zonal mean streamfunction occurring within the latitudinal zone of 0°~30°N, and index for NPO as normalized sea level pressure (SLP) difference between the region (20°N, 180°~160°W) and the region (60°N, 180°~160°W). Results show that the change of Hadley circulation is similar to that of NPO. They both exhibit apparent interannual and interdecadal variability, with a negative phase before the 1970s and a positive phase after the 1980s. In addition, there exist increasing linear trends for Hadley circulation and NPO. Hadley circulation is significantly and positively correlated to NPO on the interannual and interdecadal timescale. Due to the high comparability, the spatial structures associated with Hadley circulation and NPO are also alike over the Pacific. It is also suggested that the anomaly of the descending branch in 10°~30°N and the ascending branch in 40°~60°N over the Pacific may be responsible for the linkage of Hadley circulation to NPO.