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Fic. 12. Regression coefficients of monthly mean 500-mb height anomalies vs the Jan ENSO index from the previous Dec to the following Mar, for the MLM, NP-MLM, and control experiments. Contour interval is 10 m; positive (negative) contours are red (blue). The shading indicates two-tailed 95% statistical significance of the difference between coupled and uncoupled regressions.

Figure 12 Fic. 12. Regression coefficients of monthly mean 500-mb height anomalies vs the Jan ENSO index from the previous Dec to the following Mar, for the MLM, NP-MLM, and control experiments. Contour interval is 10 m; positive (negative) contours are red (blue). The shading indicates two-tailed 95% statistical significance of the difference between coupled and uncoupled regressions.

Related Figures (16)

Fic. 1. Schematic of the ‘‘atmospheric bridge’ between the tropical and North Pacific Oceans. The bridge concept also applies to the Atlantic, Indian, and South Pacific Oceans. The bridge occurs through changes in the Hadley and Walker cells, Rossby waves, and interactions between the quasi-stationary flow and storm tracks (see Trenberth et al. 1998). The Q,., is the net surface heat flux; w, the entrainment rate into the mixed layer from below, which is primarily driven by surface fluxes; SST the sea surface temperature; SSS the sea surface salinity; and MLD the mixed layer depth.
Fic. 1. Schematic of the ‘‘atmospheric bridge’ between the tropical and North Pacific Oceans. The bridge concept also applies to the Atlantic, Indian, and South Pacific Oceans. The bridge occurs through changes in the Hadley and Walker cells, Rossby waves, and interactions between the quasi-stationary flow and storm tracks (see Trenberth et al. 1998). The Q,., is the net surface heat flux; w, the entrainment rate into the mixed layer from below, which is primarily driven by surface fluxes; SST the sea surface temperature; SSS the sea surface salinity; and MLD the mixed layer depth.
TABLE 1. Observational studies, grouped by region, that have examined the relationship between SST anomalies in the equatorial Pacific with those elsewhere over the global oceans. Also listed is the method of analyses, the period of record, months when the anomalies peak in the non-ENSO region, lag in months from when SST anomalies peak in the equatorial Pacific and the timescales of variability examined: interannual (I), decadal (D), if differentiated. The statistical methods are abbreviated: empirical orthogonal function (EOF), singular value decomposition (SVD), singular spectrum analyses (SSA), rotated principal component analyses (RPCA), canonical correlation analyses (CCA), linear inverse modeling (LIM). * Lists additional publications that have examined observed SST relationships.
TABLE 1. Observational studies, grouped by region, that have examined the relationship between SST anomalies in the equatorial Pacific with those elsewhere over the global oceans. Also listed is the method of analyses, the period of record, months when the anomalies peak in the non-ENSO region, lag in months from when SST anomalies peak in the equatorial Pacific and the timescales of variability examined: interannual (I), decadal (D), if differentiated. The statistical methods are abbreviated: empirical orthogonal function (EOF), singular value decomposition (SVD), singular spectrum analyses (SSA), rotated principal component analyses (RPCA), canonical correlation analyses (CCA), linear inverse modeling (LIM). * Lists additional publications that have examined observed SST relationships.
Fic. 2. Correlation between SST anomalies in the ENSO region (indicated by the box in the equatorial Pacific) in NDJ with global SST anomalies in the subsequent FMA for the period 1950-99 [shading (contour) interval is 0.1 (0.2)]. The gridded SST fields were constructed from EOFs (Smith et al. 1996) prior to 1982 and optimum interpolation of surface and satellite data (Reynolds and Smith 1994) for 1982-99.
Fic. 2. Correlation between SST anomalies in the ENSO region (indicated by the box in the equatorial Pacific) in NDJ with global SST anomalies in the subsequent FMA for the period 1950-99 [shading (contour) interval is 0.1 (0.2)]. The gridded SST fields were constructed from EOFs (Smith et al. 1996) prior to 1982 and optimum interpolation of surface and satellite data (Reynolds and Smith 1994) for 1982-99.
Fic. 3. As in Fig. 2 but for the ensemble average correlation in the MLM between the NDJ ENSO index and FMA global SST anomalies for the period 1950-99 [shading (contour) interval is 0.1 (0.2)]. To properly weight the ensemble members, the gridpoint correlations from the individual simulations are first transformed into Fisher’s z statistics, averaged together, and then transformed back to correlation values.
Fic. 3. As in Fig. 2 but for the ensemble average correlation in the MLM between the NDJ ENSO index and FMA global SST anomalies for the period 1950-99 [shading (contour) interval is 0.1 (0.2)]. To properly weight the ensemble members, the gridpoint correlations from the individual simulations are first transformed into Fisher’s z statistics, averaged together, and then transformed back to correlation values.
Fic. 4. Regression values of precipitation (shaded; interval is 0.5 mm day~! °C~!) and 200-mb streamfunction (contour; interval is 1 x 10° m? day! °C!) regressed on DJF ENSO index for DJF (1951-99) for (a) observation and (b) MLM. Changes in the nondivergent component of the upper-tropospheric circulation accompanying ENSO may be inferred from the contour lines: positive (negative) extremes are associated with anomalous clockwise (coun- terclockwise) flows.
Fic. 4. Regression values of precipitation (shaded; interval is 0.5 mm day~! °C~!) and 200-mb streamfunction (contour; interval is 1 x 10° m? day! °C!) regressed on DJF ENSO index for DJF (1951-99) for (a) observation and (b) MLM. Changes in the nondivergent component of the upper-tropospheric circulation accompanying ENSO may be inferred from the contour lines: positive (negative) extremes are associated with anomalous clockwise (coun- terclockwise) flows.
Fic. 5. EOF 1 of the low-pass filtered (>~10 yr) SST during Nov-Mar from (a) observations and (b) the MLM. (c) The first PC (time series associated with EOF 1) of the filtered SST from observations (green line), the MLM (blue line), and the ENSO index (black line). The correlations (r) between the three time series are given above (c).
Fic. 5. EOF 1 of the low-pass filtered (>~10 yr) SST during Nov-Mar from (a) observations and (b) the MLM. (c) The first PC (time series associated with EOF 1) of the filtered SST from observations (green line), the MLM (blue line), and the ENSO index (black line). The correlations (r) between the three time series are given above (c).
Fic. 8. Composite El Nino — La Nina time series of SST (°C) and fluxes into the mixed layer (W m~?) over the ENSO cycle fora region in the central North Pacific (28°-42°N, 180°-160°W). (a) SST and (b) (Qn + Qg,) heat flux from NCEP reanalysis (green), the ensemble mean MLM (solid black), and the 16 individual MLM simulations (black crosses); (C) Q ne (black), Qy. (green), Q., (blue) from the MLM; and (d) the four components of Q,,.. from the MLM: Q,, (red), Qu, (blue), Q., (black), and Q;, (green). All curves have been smoothed using a three-month running average.
Fic. 8. Composite El Nino — La Nina time series of SST (°C) and fluxes into the mixed layer (W m~?) over the ENSO cycle fora region in the central North Pacific (28°-42°N, 180°-160°W). (a) SST and (b) (Qn + Qg,) heat flux from NCEP reanalysis (green), the ensemble mean MLM (solid black), and the 16 individual MLM simulations (black crosses); (C) Q ne (black), Qy. (green), Q., (blue) from the MLM; and (d) the four components of Q,,.. from the MLM: Q,, (red), Qu, (blue), Q., (black), and Q;, (green). All curves have been smoothed using a three-month running average.
Fic. 9. MLD (m) inJFM regressed on the DJF ENSO SST derived from (a) ibenice temperature measurements from White (1995) and (b) the MLM. Both are shown for 1956-96, the period when observations are available.
Fic. 9. MLD (m) inJFM regressed on the DJF ENSO SST derived from (a) ibenice temperature measurements from White (1995) and (b) the MLM. Both are shown for 1956-96, the period when observations are available.
Fic. 10. El Nifo — La Nina composite of SST over the North Pacific in Feb(1)-Mar(1), Aug(1)-Sep(1), and Dec(1)-Jan(2) from (left) observations and (right) the ensemble mean MLM. (bottom) The observed El Nifo — La Nina composite SST in the tropical Pacific in Dec(1)-Jan(2). The shading (contour) interval is 0.1 (0.2) °C.
Fic. 10. El Nifo — La Nina composite of SST over the North Pacific in Feb(1)-Mar(1), Aug(1)-Sep(1), and Dec(1)-Jan(2) from (left) observations and (right) the ensemble mean MLM. (bottom) The observed El Nifo — La Nina composite SST in the tropical Pacific in Dec(1)-Jan(2). The shading (contour) interval is 0.1 (0.2) °C.
Fic. 11. The composite E] Nino — La Nifa ocean temperature from Nov(0) to Jun(2) and the composite MLD (m) during El Nino (solid red line) and La Nina (solid green line) from the MLM in the central North Pacific region.
Fic. 11. The composite E] Nino — La Nifa ocean temperature from Nov(0) to Jun(2) and the composite MLD (m) during El Nino (solid red line) and La Nina (solid green line) from the MLM in the central North Pacific region.
Fic. 13. Time series of the warm — cold composite of the 30-day running mean 500-mb height anomalies averaged over a box centered in the North Pacific (32°-48°N, 176°E-142°W) for all three experiments. Open circles indicate 95% significance of the differences between the anomalies in MLM or NP-MLM and the control, while full circles indicate significant differences between anomalies in the NP-MLM and MLM.
Fic. 13. Time series of the warm — cold composite of the 30-day running mean 500-mb height anomalies averaged over a box centered in the North Pacific (32°-48°N, 176°E-142°W) for all three experiments. Open circles indicate 95% significance of the differences between the anomalies in MLM or NP-MLM and the control, while full circles indicate significant differences between anomalies in the NP-MLM and MLM.
Fic. 14. Warm (El Nino) and cold (La Nifia) composites of monthly mean 500-mb North Pacific height anomalies in all three experiments (averaged over the same box as in Fig. 13), for all members in each experiment during Jan, Feb, and Mar of Y r(1). The black crosses indicate the ensemble averages, while the black circle indicates the observed composite value.
Fic. 14. Warm (El Nino) and cold (La Nifia) composites of monthly mean 500-mb North Pacific height anomalies in all three experiments (averaged over the same box as in Fig. 13), for all members in each experiment during Jan, Feb, and Mar of Y r(1). The black crosses indicate the ensemble averages, while the black circle indicates the observed composite value.
Fic. 15. Sensitivity map, or influence function, of a negative height anomaly over the North Pacific to anomalous SSTs 60 days earlier in the MLM. The influence function is contoured at an interval of 0.002 K m~'; the zero contour is removed for clarity and positive (negative) values are red (blue). The target height response at 200 mb is indicated by gray shading with a 0.25-m interval.
Fic. 15. Sensitivity map, or influence function, of a negative height anomaly over the North Pacific to anomalous SSTs 60 days earlier in the MLM. The influence function is contoured at an interval of 0.002 K m~'; the zero contour is removed for clarity and positive (negative) values are red (blue). The target height response at 200 mb is indicated by gray shading with a 0.25-m interval.
Fic. 16. (a) MLM minus control and (b) NP-MLM minus control warm — cold composite tropical precipitation during Feb(1). Contour (shading) interval is 0.1 (0.05) cm day~!. (c) Warm — cold composite of the 30-day running mean precipitation (cm day~!) in the MLM, NP-MLM, and control experiments averaged over the regions shown in (b): the central (5°- 15°S, 170°E-150°W) and western (5°S-5°N, 120°-160°E) equatorial Pacific. Precipitation anomalies in the central (western) Pacific are shown by solid (dashed) lines; open circles indicate that the differences between the anomalies in the MLM or NP-MLM and the control are significant.
Fic. 16. (a) MLM minus control and (b) NP-MLM minus control warm — cold composite tropical precipitation during Feb(1). Contour (shading) interval is 0.1 (0.05) cm day~!. (c) Warm — cold composite of the 30-day running mean precipitation (cm day~!) in the MLM, NP-MLM, and control experiments averaged over the regions shown in (b): the central (5°- 15°S, 170°E-150°W) and western (5°S-5°N, 120°-160°E) equatorial Pacific. Precipitation anomalies in the central (western) Pacific are shown by solid (dashed) lines; open circles indicate that the differences between the anomalies in the MLM or NP-MLM and the control are significant.
Related topics:
OceanographyAtmospheric sciencesAir-Sea InteractionAtmospheric CirculationSouthern OscillationNorth Pacific OceanMixed layer
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