Earth's rotation and high frequency equatorial angular momentum budget of the atmosphere

The effect of the atmosphere on the Earth's rotation can be computed by two different but fundamentally equivalent approaches. The more commonly used is the so-called angular momentum approach, and the second is the torque ap proach. Their physical meanings are recalled, and numerical results from th e two are intercompared, concentrating on the lowest periods of a few days or shorter. The indirect effect of the atmosphere on the Earth rotation due to atmospheric forcing on the ocean is also described based on both static and dynamic oceanic models. Results are discussed for the equatorial compo nents and for the highest frequencies.