Transcript Document
La prevision saisonniere avec l’outil CPT By: Ousmane NDIAYE Niamey, Niger, 1st June 2007 Les bases de la prevision saisonnieres? Forcage de la SST sur le climat Ocean 2/3 de la surface de la terre forte capacite thermique : source de vapeur d’eau precipitable Dynamique : circulation –El Nino Rationale for seasonal prediction: slower evolution of the oceanic component of the climate sytem SST on tropical atmosphere Comment cela marche alors ? Observed Rainfall/crop yield SEA SURFACE TEMPERATURE SEA SURFACE TEMPERATURE Ocean STATISTICAL RELATIONSHIP PREDICTION : Rainfall, humidity… Atmospheric General Circulation Model ATMOSPHERIC CONDITIONS Atmosphere Coupled Ocean and Atmosphere GCM Ocean Atmosphere SST AGCM Observed : yield/rainfall Atmospheric conditions Ocean conditions Model Output Statistics (Statistical Correction) Modele de prevision statistique: regression Comment ca fonctionne ? time Predictand (rainfall) Y Predictor (SST) X Y50 Y51 Y52 Y53 Yk-1 Yk Yk+1 Y96 Y97 Y98 Y99 X50 X51 X52 X53 Xk-1 Xk Xk+1 X96 X97 X98 X99 Tres tres simple : Periode 1 Y = a*X + b (a,b) ? Periode 2 a*X + b observee Ŷ+e prevue La Validation croisee sur une fenetre d’une annee 1951 1952 1953 1954 1955 Predict 1951 Training Predict period 1952 Training Predict period 1953 Training period Training period Training period Training Period Training period Predict Training 1954 Period Predict Training 1955 period … après correle 1951–2000 observee vs prevue. Prevision Retro-spective/active 1981 1982 1983 1984 1985 Training period Predict (1951-1980) 1981 Training period Predict (1951-1981) 1982 Training period (1951-1982) Training period (1951-1983) Training period (1951-1984) Omit 1982+ Omit 1983+ Predict 1983 Omit 1984+ Predict Omit 1984 1985+ Predict 1985 Climate Predictability Tool : CPT OVERVIEW The Climate Predictability Tool (CPT) provides a Windows package for : seasonal climate forecasting model validation actual forecasts given updated data Uses ASCII input files : GCM, Stations, Indices Options : principal components regression (PCR) canonical correlation analysis (CCA) Help Pages on a range of topics in HTML format Options to save outputs in ASCII format and graphics as JPEG Program source code is now available for those using other systems (e.g., UNIX) CPT INPUT FILE FORMATS 1. STATION files: This file-type contains : Station_name (without spaces; 16 characters) Latitude (in signed degrees) Longitude (signed degrees) Year (in the first column) Data (missing values should be filled with the same value, -9999 for example) Keywords: STN, LAT, LONG CONCLUSIONS • For further details, read the help page of each menu and option. • Subscribe to the user-list to be advised of updates: http://iri.columbia.edu/outreach/software/ • We want to hear from you. Your comments and questions help us to improve the CPT so do not hesitate to write to us at: [email protected]