Wind profiler yields observations of ENSO signal

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Abstract

Nearly continuous observations of tropospheric wind at Christmas Island (2°N, 157°W) have been made since March 1986 using a VHF wind-profiling Doppler radar. The interannual zonal wind variations observed at this central Pacific location show a clear El Niño/Southern Oscillation (ENSO) signal with weaker than normal lower tropospheric easterlies and upper tropospheric westerlies during El Niño and stronger than normal lower tropospheric easterlies and upper tropospheric westerlies during La Niña. These dramatic changes in the tropospheric circulation over the central Pacific are related to variations in the zonal Walker Circulation, which in turn are associated with the Southern Oscillation. Observations recorded from 1986 to 1989 illustrate a complete ENSO cycle with the 1986–1987 El Niño followed by the 1988–1989 La Niña.