La prevision saisonniere avec loutil CPT By Ousmane
La prevision saisonniere avec l’outil CPT By: Ousmane NDIAYE Niamey, Niger, 1 st June 2007
Les bases de la prevision saisonnieres?
Forcage de la SST sur le climat E Ocean 2/3 de la surface de la terre E forte capacite thermique : E source de vapeur d’eau precipitable E 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 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 Ø Atmospheric conditions Ø Ocean conditions Model Output Statistics (Statistical Correction)
Modele de prevision statistique: regression
Comment ca fonctionne ? time Predictand (rainfall) Y Predictor (SST) X Y 50 Y 51 Y 52 Y 53 Yk-1 Yk Yk+1 Y 96 Y 97 Y 98 Y 99 X 50 X 51 X 52 X 53 Xk-1 Xk Xk+1 X 96 X 97 X 98 X 99 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
Prevision Retro-spective/active
Climate Predictability Tool : CPT
OVERVIEW The Climate Predictability Tool (CPT) provides a Windows package for : Ø seasonal climate forecasting Ø model validation Ø actual forecasts given updated data Uses ASCII input files : GCM, Stations, Indices Options : Ø principal components regression (PCR) Ø 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: cpt@iri. columbia. edu
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