Spatial and Temporal Variations of Global Mountain Torque and Relations to Earth’s Rotation

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 fi ve 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.