1. Pacific SST Variability 1900-2002: Structure and Evolution Bin Guan & Sumant Nigam Department of Atmospheric and Oceanic Science University of Maryland, College Park 11 th Annual CCSM Workshop, Breckenridge, CO; 20-22 June, 2006

2. Pacific SST Analyses Deser & Blackmon 1995 Zhang et al. 1997 Mantua et al. 1997 Nakamura et al. 1997 Nigam et al. 1999 Barlow et al. 2001 Wu et al. 2003 …And others

3. Analysis Issues Short records Data pre-filtering, de-trending Regional analysis domain Single season analysis Spatial pattern recurrence is targeted Techniques vary (corr/covar; rot/unrot)

4. GOAL Obtain a robust characterization of all non-seasonal modes of Pacific SST (ocean-atmosphere) variability from a single analysis of unfiltered data.

5. Extended EOF Analysis Targets both spatial and temporal recurrence No temporal periodicities are imposed EEOF differs from EOF only in anomaly definition: EOF: ψ(x,y,t o ) EEOF: […,ψ(x,y,t o -Δt), ψ(x,y,t o ), ψ(x,y,t o +Δt),…] Δt was chosen to be a season Temporal recurrence analyzed with a 1-year window (5 staggered data bands) 1900-2002 Hadley SSTs analyzed; all-season analysis Analysis domain: Pan Pacific (120E-60W; 20S-60N) EEOFs are rotated

6. ENSO − (REEOF2; 13.6%)ENSO + (REEOF1; 17.7%) ENSO

7. ENSO PCs (PC1&2)

8. Trend mode (REEOF3; 10.2%)Linear trend Trend

9. 1951—2002 precipitation (CRUTS2.1) mm day -1 Trend Mode’s Regressions on African/Asian Precipitation mm day -1

10. PDV Pan-Pacific (REEOF4; 5.3%)PDV North Pacific (REEOF6; 4.3%) Pacific Decadal Variability (PDV)

11. PDV Pan-Pacific (PC4)

12. PDV North Pacific (PC6)

13. Summary Analysis features - Pan-Pacific analysis domain - all seasons included - unfiltered data - rotated extended EOF - sensitivity tests (domain/period analyzed, number of EEOFs rotated, etc.) ENSO, PDV, trend (and other modes of interest) simultaneously extracted Two modes relevant to PDV: Pan-Pacific, North Pacific

14. Future Plans Analysis of subsurface data; PDV mechanisms Attribution of 20 th century climate anomalies (e.g., the Dust Bowl drought) to the various low-frequency modes Model intercomparisons: how are the modes and their impacts on climate represented in coupled models?

15. Biennial (REEOF7; 3.5%)Non-canonical ENSO? (REEOF5; 4.3%) Appendix