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An Attribution Analysis of CPC Seasonal Surface Temperature Forecast Skill. Peitao Peng Arun Kumar Climate Prediction Center 32 nd CDPW, Tallahassee, FL Acknowledgments: M. Halpert, D. Unger and B. Jha. Outline.
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An Attribution Analysis of CPC Seasonal Surface Temperature Forecast Skill Peitao Peng Arun Kumar Climate Prediction Center 32nd CDPW, Tallahassee, FL Acknowledgments: M. Halpert, D. Unger and B. Jha
Outline • Heidke skill score (HSS) of seasonal surface temperature forecast for the period of 1995-2007; • Analysis of dominant predictors; • Analysis of individual tools and their consolidation; • Thoughts on the future skill improvement.
Heidke Skill Score (HSS) of CPC Seasonal Temperature Forecast (95-07) (0-mon Lead) HSS=100x(H-N/3)/(N-N/3) H: hit number N: total case number
How are the skill variations related to dominant predictors (i.e., tropical SST and recent trend in surface temperature)?
Conclusion 1: Temperature trend dominates over the tropical SSTs in explaining the skill.
More evidence about the dominance of the trend: An analysis of the HSS over the southwest region of US
Skill Analysis for the Southwest US HSS vs Nino3.4: COR=0.05 HSS vs sfcT: COR=0.83
Temperature trend The similarity of the trend map (right) with the HSS map shows that most skill indeed comes form the trend prediction
Analysis of individual tools • CFS: NCEP climate forecast system • OCN: optimal climate normal • CCA: canonical correlation analysis • SMLR: screening multiple linear regression
HSS of Individual Models (temporal variation) CCA: 9.3 OCN: 19.5 SMLR: 8.4 CFS: 12.7
HSS of Individual Models (spatial distribution) OCN CCA SMLR CFS
Individual Model HSS vs Nino3.4 Amplitude OCN: cor=0.2 CCA: cor=0.2 SMLR: cor=0.27 CFS: cor=0.25
Individual model HSS vs US T CCA: cor=0.48 OCN: cor=0.84 SMLR: cor=0.44 CFS: cor=0.77
Consolidated vs Official: spatial distribution of HSS Consolidation Official
Consolidated vs individual tools Skills: CONS(18.1); OCN(19.5); CFS(12.7); CCA(9.3); SMLR(8.4)
Conclusion 2: • Recent temperature trendis a major skill source for all the forecast tools analyzed here; • OCN dominates over other tools in US seasonal forecast; • CFS can catch the trend information as well, Land initial conditions? Something else? • The skill of the consolidation toolmostly from the OCN.
Perspectives on forecast skill improvement in the future • Next generation CFS with improved ICs is expected to be more skillful in forecasting ENSO and variability related to other physical process; • Improvement of OCN with some techniques (EOCN, EMD); • Multi-model ensemble (MME); optimal schemes for MME.