Global propagation of interannual fluctuations in atmospheric angular momentum

A study is presented of the latitudinal redistribution of angular momentum within the atmosphere from 1976 to 1991. Slow global-scale coherent poleward propagation of atmospheric angular momentum fluctuations are observed on interannual timescales. These originate in equatorial regions, where they lead the main atmospheric anomalies of the ENSO cycle by nearly two yrs; they penetrate to latitude higher than 60 deg in both hemispheres, where they lag behind the ENSO cycle by about four yrs. The bimodality of the ENSO phenomenon, with a low-frequency component centered at a period close to 4.2 yrs and a high-frequency component centered near 2.4 yrs, can also be distinguished. Each of the two components has a distinct latitudinal propagation pattern.