Refined correlations between atmospheric and rapid polar motion excitations

Abstract

SUMMARY In this work we employ Monte Carlo experiments to explore reports by others of a statistically significant correlation between atmospheric angular momentum variations and polar motion on timescales of days to months. Our experiments verify that the correlation between atmospheric and geodetic excitation is statistically diVerent from zero at the 0.997 confidence level, and demonstrate that the correlations improve with more recent recreations of the older data sets. Additional Monte Carlo experiments reveal that, during the previous decade, about 60 per cent of the atmospheric excitation was eVective in exciting rapid polar motion, and nearly 80 per cent of the geodetic excitation was atmospheric in origin on these timescales; with the older data sets, barely 50 per cent of the geodetic excitation could be ascribed to an atmospheric origin. Possible sources of the remaining polar motion excitation are briefly discussed. Our work implies that simply subtracting atmospheric angular momentum from geodetic data may not be the best way to remove the atmospheric contribution. We also present the first correlation results employing atmospheric excitation data corrected for the dynamic response of the oceans to barometric pressure forcing.