Kessler and McPhaden, 1995b Abstract

The 1991-93 El Niño in the central Pacific

Kessler, W.S. and M.J. McPhaden, 1995

Deep-Sea Research II, 42, 295-333.

The 1991-93 El Niño event is described using data from the TOGA-TAO buoy network, concentrating on variability at 140W where a full suite of temperature, current, and surface meteorological observations were made. The daily time series furnished by the buoy array brings out the conspicuous importance of remotely forced intraseasonal variability in the form of equatorial baroclinic Kelvin waves during the evolution of the 1991-93 El Niño. Notable variations along 140W included a major weakening of the Equatorial Undercurrent in late 1991-early 1992, and a reduction in intensity of monthly period tropical instability waves during the latter part of 1991 compared to previous non-El Niño years. The North Equatorial Countercurrent showed no major signal due to this El Niño, in contrast to earlier warm events. Although anomalies of the South Equatorial Current spanning the equator were in an eastward sense during the height of the event, the result of these changes was that near- surface flow across 140W between 5S and 5N was close to zero, so there was apparently no large eastward transport of surface water past 140W into the eastern equatorial Pacific. The relative phasing of anomalies of thermocline depth, equatorial undercurrent speed and SST during the warm event of 1991-92 was somewhat similar to that seen during the 1986-87 El Niño, although the earlier event was followed by a strong cold (La Nina) event whereas the recent one was not. Uniquely among modern El Niño events, after the 1991-92 episode appeared to end with a reappearance of the equatorial cold tongue in mid-1992, a second SST warming in the eastern Pacific occurred in early 1993.
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