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Pacific SST Variability 1900-2002: Structure and Evolution

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. Pacific SST Analyses. Deser & Blackmon 1995

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Pacific SST Variability 1900-2002: Structure and Evolution

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  1. Pacific SST Variability 1900-2002: Structure and Evolution Bin Guan & Sumant Nigam Department of Atmospheric and Oceanic Science University of Maryland, College Park 11th 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,to) EEOF: […,ψ(x,y,to-Δt), ψ(x,y,to), ψ(x,y,to+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 ENSO− (REEOF2; 13.6%) ENSO+ (REEOF1; 17.7%)

  7. ENSO PCs (PC1&2)

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

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

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

  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 20th 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. Appendix Biennial (REEOF7; 3.5%) Non-canonical ENSO? (REEOF5; 4.3%)

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