Geophysical Research Letters
Supporting Information for
Atmospheric Response to the North Pacific Enabled by Daily Sea Surface
Temperature Variability
Guidi Zhou 1 , Mojib Latif 1,2 ,*, Richard J. Greatbatch 1,2 , Wonsun Park 1
1 GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, D-24105 Kiel, Germany
2 University of Kiel, Kiel, Germany
* Corresponding author address: Prof. Dr. Mojib Latif, Ocean Circulation and Climate Dynamics Division,
GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany.
Email: mlatif@geomar.de
Figures S1 to S10
We show in Figures S1 and S2 additional material from the observational analyses.
Figures S3-S6 depicts some characteristics of the SST forcing which was applied to the atmosphere model. Figure S7 shows the storm track response. Figure S8 shows the probability density function of SST gradients in the experiments. Figure S9 depicts the vertical profile of the Eady growth rate and linked quantities. Figure S10 shows horizontal maps of the latent heat flux response.
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(a) Lag 2 – SST (b) Lag 2 – SLP
(c) Lag 3 – SST (d) Lag 3 – SLP
Figure S1: Same as Figure 1 but for further lags at (a, b) 2 (c, d) 3 years.
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Figure S2: Cross-correlation between the leading PC of North Pacific SLP and the
ENSO-removed PDO index. Positive lag means the PDO index leads. The PCs and correlations are based on monthly data. Time lags being multiples of 12 months are denoted by dots. The 95% significance level is shown by the red horizontal lines.
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Figure S3: Positive phase of the winter (DJF) mean pattern of the daily SST anomaly forcing in the North Pacific [°C]. No SST anomaly is present in other basins.
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Figure S4: NOAA-OI-SST observation at Jan 1st, 1984 (red solid contours;
DAGL/DANP), the 11day filtered SST (red dashed contours; FILT), the “high-frequencyplusclimatological” SST (black dashed contours; HFCL), and the 1981–1990 daily climatology (black solid contours; CLIM) for the same calendar day [°C].
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Figure S5: Time series of wintertime (DJF) SST [°C] averaged over 145°E–150°E,
35°N–42.5°N (indicated by the box in the inset) from the NOAA-OI-SST daily observations. The red and blue dotted curves represent the 1984 –85 and 1990–91 winters (DAGL/DANP) respectively, whereas the smooth red and blue curves are the 11day running means of the same winters (FILT). The black dotted curve shows the “highfrequency-plusclimatological” SST (HFCL), and the smooth black curve is the 10-year daily climatology (CLIM).
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(a) Field STD (b) Sub-monthly STD
Figure S6: 10year time series of (a) winter mean field STD [°C] indicating the level of spatially small-scale variability. It is the spatial STD of SST difference from the 10-year daily climatology computed using every ocean grid point in the North Pacific (120 °E–
100 °W, 10°N–60°N). (b) winter-mean sub-monthly STD [°C] indicating the level of temporally high-frequency variability computed after subtracting the linear trend within each month. The variability in CLIM and HFCL is due to leap years.
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(a) DANP (b) CLIM
(d) HFCL (c) FILT
Figure S7: 10-year mean winter (DJF) storm track [m] response at 500 hPa simulated in
(a) DANP, (b) CLIM, (c) FILT, (d) HFCL. Storm track is defined as the standard deviation of band-pass (2 –8 days) filtered geopotential heights. Statistical significance at the 90% level is indicated by hatching.
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(a) PDF (b) PDF: high gradient
Figure S8: Probability density function (PDF) of the magnitude of 2-dimensional SST gradients over (a) the whole gradient range and (b) the high gradient range
(≥1°C/100km). Note that in (b), bars within each group have the same gradient value.
Gradients are computed by comparing adjacent grid points. The PDF is computed over all grid points in the North Pacific and at all time steps during the 10 winters.
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(a) Eady growth rate (b) Brunt-Väisälä frequency
(c) Vertical wind shear (d) flux
h
·eddy heat
Figure S9: Vertical profiles of the 10-year mean winter (DJF) response of (a) Eady growth rate [10 6 s -1 ], (b) BruntVäisälä frequency [10 3 s -1 ], (c) vertical wind shear [10 4 s -1 ],
(d) divergence of eddy heat flux [°C/day] averaged over the area 30°N–40°N, 120°N–
180°N.
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(a) DANP
(c) FILT
(b) CLIM
(d) HFCL
(e) T31
Figure S10: 10-year mean winter (DJF) surface latent heat flux [W/m 2 ] response
(downward positive) simulated in (a) DANP, (b) CLIM, (c) FILT, (d) HFCL, and (e) the
T31 experiment. Statistical significance at the 90% level is indicated by hatching.
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