Changes in the globally integrated angular momentum of the atmosphere from 1983 to 1987 were computed from Fleet Numerical Oceanography Center wind analyses and compared to astronomically measured changes in length of day obtained from the U.S. Naval Observatory. In agreement with previous studies, the two time series are highly coherent and in phase at periods ranging from 40 days up to the longest periods that are resolved by the data. By examining the contribution to the global atmospheric angular momentum from the tropical and extratropical regions separately, it is found that fluctuations in the Earth's angular momentum and length of day at subseasonal periods of 50--100 days are dominated by wind changes in the tropics. ¿ American Geophysical Union 1988