全球山脉力矩时空变化及其与地球自转的关系
Spatial and Temporal Variations of Global Mountain Torque and Relations to Earth’s Rotation
中文摘要：
山脉力矩是大气轴向角动量变化的主要外部因子之一，是研究地球运动和大气相互作用的关键变量。利用NCEP/NCAR第一套再分析资料计算了1948—2011年的全球山脉力矩，定量分析了全球山脉力矩的时空变化趋势及其与地球自转速率（以日长表示）的关系。研究表明，近64年山脉力矩变化最为显著的地区集中在青藏高原和南美的安第斯山脉，青藏高原东西两侧的山脉力矩具有不同的变化趋势。滞后相关分析显示，全球山脉力矩与日长的相关系数在日长滞后5年时达到最大（滞后相关系数为-0.482），而南美安第斯山和青藏高原的山脉力矩则分别于日长滞后2年和9年时达到最大（滞后相关系数分别为-0.461和-0.689），因此山脉力矩的变化早于日长变化。从年代际变化看，全球积分的山脉力矩和南亚高压强度指数趋势上基本一致, 可以作为表征天气、气候变化的一个强信号。
中文关键词：
山脉力矩，日长，时空变化，地球自转，变化趋势
KeyWords：
mountain torque, length of day, spatial-temporal variation, Earth’s rotation, long-term trend
Abstract：
Mountain torque is an important external factor influencing the dynamics of axial atmospheric angular momentum and it also plays a major role in the interaction between the Earth and the atmosphere. Using the data from NCEP/NCAR reanalysisⅠ, the daily global mountain torque during the period from 1948 to 2011 is calculated. Spatial and temporal variations of mountain torque and its relations to variations of earth rotation rate (denoted as length of day, LOD) are further discussed. It is shown that Tibetan Plateau located in East Asia and the Andes located in South America are two main areas with significant mountain torque change during the past 64 years. Mountain torque at east and south sides of Tibetan Plateau has different trends. Moreover, mountain torque and LOD are lag correlated. Maximal correlation occurred respectively when global mountain torque leads LOD five years (R=－0.482), Andes Mountain torque leads LOD two years (R=－0.461) and Tibetan Plateau mountain torque leads LOD nine years (R=－0.689), suggesting that mountain torque forces LOD anomalies. On a decadal scale, global mountain torque has a similar trend with intensity index of South Asian High, indicating that mountain torque can be a very useful signal for climate change.