Supplemental Figuresfor
Quantifying and Understanding Forced Changes to Unforced Modes ofAtmospheric Circulation Variability over the North Pacific in a Coupled
Model Large Ensemble
John P. O’Brien* 1,2
Clara Deser 1
1 Climate and Global Dynamics Division

National Center for Atmospheric Research, Boulder, CO
2 Climate and Ecosystem Sciences Division

Lawrence Berkeley National Laboratory, Berkeley, CA

Submitted to J. Climate, 11 Feb 2022
Revised, 30 May 2022
* Corresponding author: Dr. John. P. O’Brien, jpobrien@ucar.edu

Figure S1: DJF Z500 regressions (color shading; m) during 1923-1933 (left) and 2088-2098(right) for the 3 leading SEOFs of North Pacific Z500 variability (top 3 rows) and the leading
SEOF of North Atlantic Z500 variability (bottom row). Stippling indicates statistically significantvalues (99th percentile confidence level) in at least 7 of 10 years. Red boxes show the domains
over which the modes are calculated.

Figure S2: (e-l): As in Fig. S1 but for TS (°C; color shading) and Z500 (contour interval = 10m;
negative values shown as dashed contours). (a-d) Regressions based on the two leading SEOFs ofTropical Pacific SST variability (red boxes show the domains over which the modes arecalculated).

Figure S3: Scatter plots of all modes considered in this study plotted against TPac_TS_SEOF1(left pane) and TPac_TS_SEOF2 (right pane). Each column corresponds to the data representing
the first 30 years (early) and the last 30 years (late) periods. Axes and aspect ratios are set suchthat the 1-to-1 lines are the 45 degree diagonal bisecting each panel.

Figure S4: Fraction of variance explained for the SEOFs used in this study with associated North
Test Errors plotted as filled shading. Top panel: TPac Domain; Middle panel: NPac Domain;
Bottom panel: NAtl Domain. The lowest order SEOF shown for each domain is the first SEOF
excluded for this study. We show the first excluded SEOFs here to allow for comparison (in termsof separation in variance explained space) to the last included SEOFs.

Figure S5: As in Fig. S1, but for the first two SEOFs of tropical SST variability (see panels a andb in Fig. S2 for domains of the SEOF calculations).

Figure S6: Correlations for each pair of SPCs defined in the main text.

Figure S7: As in Fig. S1 after removal of the two leading SEOFs of tropical Pacific SSTvariability.

Figure S8: Distribution of (a) pattern correlations and (b) rmse between precipitation regression
maps for each Z500 SEOF mode during 1923-1933 (full fields in blue and tropical-residual fieldsin red) against the corresponding EOF mode from the atmosphere-only control simulation (circles:<5th and > 95th percentiles; whiskers: 5th-to-95th percentiles; box: 25th-to-75th percentiles; blacknotch in box: 50th percentile). 10,000 samples were generated for each EOF mode of the 2600year atmosphere-only control simulation by randomly resampling 200 years (withoutreplacement).

Figure S9: Probability distributions for each of the modes included in this study. Blue/red
distributions correspond to the first/last 30 years of the 1921-2100 analysis period. Blue/red
vertical lines indicate the 10th and 90th percentiles of the early/late distributions.

Figure S10: Early period (first 30 years) composites of the four extratropical modes considered inthis study (rows) according to where their respective SPCs exceed the 90th percentile (leftcolumn), the 10th percentile (middle column), and their sum (right column). Color-filled data show
the DJF temperature anomaly. Solid/dashed black contours denote positive/negative Z500 heights
at 10 meter intervals ranging from -150 to 150 meters.

Figure S11: As in Fig. S10, but for precipitation.

Figure S12: As in Fig. S10, but for data corresponding to the late period (last 30 years).

Figure S13: As in Fig. S11, but for data corresponding to the late period (last 30 years).

Figure S14: As in Fig. S10, but for the two tropical Pacific modes.

Figure S15: As in Fig. S11, but for the two tropical Pacific modes.

Figure S16: As in Fig. S12, but for the two tropical Pacific modes.

Figure S17: As in Fig. S13, but for the two tropical Pacific modes.