FY 1985

The vertical structure of the zonal pressure gradient in the eastern equatorial Pacific

Mangum, L.J., and S.P. Hayes

J. Geophys. Res., 89(C6), 10,441–10,449, doi: 10.1029/JC089iC06p10441 (1984)

CTD data from the EPOCS and NORPAX experiments were used to construct a mean zonal pressure gradient profile between 110°W and 150°W for the 1979 to 1981 pre-El Niño time period. The mean zonal pressure gradient referenced to 100 dbar had a value of at the surface and decreased to within two standard errors of zero at 200 dbar. Below this depth the mean was not significantly different from zero. Deviations from this mean were not related to fluctuations of the zonally averaged zonal wind stress between 150°W and 110°W. Rather, the largest deviations, in the boreal springs of 1979 and 1980, appeared to be associated first with vertical-mode Kelvin wave pulses propagating eastward along the equator. The 1979–81 mean profile was also used as a reference to examine variations in zonal pressure gradient during the 1982/83 ENSO event. The sea surface was more sharply sloped upward from the east to west in beginning of the event. The surface slope was below normal in April and October 1983. Vertical profiles of the zonal pressure gradient deviations showed larger high vertical-mode contributions during the vent than in the prevent samples.