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Variability of the sea surface temperature in the eastern equatorial Pacific during 1986-88

S.P. Hayes

Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration, Seattle, Washington

Ping Chang

Joint Institute for the Study of the Atmosphere and Ocean, Department of Atmospheric Sciences, University of Washington, Seattle, Washington

M.J. McPhaden

Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration, Seattle, Washington

Journal of Geophysical Research, 96(C6), 10,533-10,566 (1991)
Copyright ©1991 by the American Geophysical Union. Further electronic distribution is not allowed.

Gallery of Figures

Figure 1. Depths and locations of the time series used in this study. (Top) Record lengths of the velocity (u) and temperature (T) time series at 0, 110W. (Bottom) SST and wind record lengths at the measurement locations along 110W. SST was measured at 1 m depth except at 5S for January-August 1986, when the 20 m temperature record was used.

Fig. 2. Time series of zonal and meridional surface wind, SST, and depth of the 20C isotherm at 0, 110W for the 3 years 1986-1988. Solid lines are the measured values, and dotted lines are the monthly mean climatological values based on the historical data from the mooring at this location [McPhaden and Hayes, 1990].

Figure 3. Low-pass-filtered (91-day Hanning filter) time series of the SST (T, solid line), surface wind speed (U, short-dashed line), and total surface heat flux (Q, long-dashed line, see text) at 0, 110W for the period indicated. The mean value has been removed from each series prior to plotting. Scales for Q are on the left-hand axis; T and U are indicated on the right.

Figure 4. Components of the surface heat flux (see equation (1)).

Figure 5. Contour plots of (a) isotherm depth (contours are in degrees Celsius), (b) zonal velocity (centimeters per second), and (c) meridional velocity (centimeters per second) in the upper 100 m at 0, 110W, based on the 91-day low-pass-filtered time series. The dashed line superimposed on the isotherm contours indicates the mixed layer depth computed as discussed in the text. Contour intervals are 1C, 20 cm s, and 5 cm s for temperature, zonal velocity, and meridional velocity, respectively.

Figure 6. Time series plots of various terms in equation (1). All time series have been low pass filtered with a 91-day Hanning filter. (a) Change in the mixed layer heat content, Q; the solid line was computed with variable h, and the dashed line has a constant h = 25 m. (b) Zonal advective heat flux, Q; the solid line was computed with T/x estimated from moorings at 110W and 140W, dashed line assumes a constant . (c) Vertical entrainment, Q. (d) Vertical diffusive heat flux, Q. (e) Superposition of Q (dashed line) and Q (solid line) as defined in the text.

Figure 7. Low-pass-filtered (91-day Hanning filter) time series of the mixed layer depth h and Richardson number Ri at the base of the mixed layer at 0, 110W, estimated as described in the text.

Figure 8. Time series of the winds, SST, and depth of the 18C isotherm for boreal spring of (a) 1986, (b) 1987, and (c) 1988 at the latitudes indicated along 110W. Wind sticks point in the direction toward which the wind is blowing. The length of the sticks is such that 20 m s is equivalent to the monthly tick marks on the time axis. For SST and 18C depth, the light line indicates the daily data and the heavy line indicates a 21-day Hanning low-pass filter. The 5S SST in 1986 is actually the 20-m temperature record. The SST and 18C depth scales are correct for the equatorial time series. The SST time series at the other latitudes have been offset as follows: 5N and 2N are offset by 6C and 3C for all 3 years shown, 2S is offset by -3C in 1987 and by -6C in 1988, and 5S is offset by -6C in 1986 and 1987 and by -10C in 1988. The 18C time series offsets are the same in all years: 5N is offset by -125 m, 2N by -50 m, 2S by 50 m, and 5S by 75 m.

Figure 9. Meridional structure functions and time series of the first EOF of surface relative to 300 dbar dynamic height constructed from the temperature time series along 110W in 1987 and 1988. For comparison the meridional structure of a first-vertical-mode equatorial Kelvin wave with a phase speed of 2.1 m s is also shown.

Figure 10. Time series of zonal and meridional velocity on the equator at 110W at depths of 10 m (light line), 45 m (heavy line), and 120 m (dashed line) for boreal spring of 1986, 1987, and 1988. Units of velocity are centimeters per second.

Figure 11. The top panel for each year shows time series (45-day low-pass Hanning filter) of Q (dashed) and Q (solid; see text for definition). The bottom panel for each year shows meridional diffusive heat flux Q (dashed) and meridional advective heat flux Q (solid). Records for boreal spring 1986, 1987, and 1988 are shown.


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