Recently discovered small polar motion loops and their atmospheric excitation mechanism

摘要

Polar motion is the relative motion of the solid Earth with respect to its rotational axis. Recently, small loops have been discovered in unfiltered polar motion observations. These loops with periods less than 21 d and sizes ranging from a silver dollar coin to a compact disc (when projected onto the surface of the Earth) are currently observable because every ～6.4 years the Chandler, annual, and semiannual variations that dominate this motion destructively interfere and act like a high-pass filter. These loops, as well as diurnal polar motion variations, are shown to be significantly correlated to variations in atmospheric angular momentum that result primarily from rapid fluctuations in atmospheric pressure fields with the contributions from the winds playing a smaller variable role. Finally, the results show that variations in the speed of weather patterns and whether or not the surface winds are interacting with land or oceans have an effect on polar motion that is observable with current geodetic observational techniques.