Annual atmospheric torques: Processes and regional contributions

[1] All three components of annual atmospheric torque are analyzed with a focus on understanding the contributions from various sources and the physical interactions involved. The annual variations of the equatorial component are dominated by the torque on Earth's ellipticity, with the X component mainly due to an anomaly over the Himalayas, and the Y component associated with pressure anomalies over the North Pacific Ocean. The axial annual component is due to the combined effect of friction and mountain torque, whose amplitudes are at the same order of magnitude with the friction term being larger. Partial cancellation of the mountain torque over Asia and North America is effected by the out-of phase contribution of the Andes (South America having the opposite seasonal cycle to Asia and North America).