title: Exploratory analysis of climate data using source separation methods.
abstract: We present an example of exploratory data analysis of climate measurements using a recently developed denoising source separation (DSS) framework. We analyzed a combined dataset containing daily measurements of three variables: surface temperature, sea level pressure and precipitation around the globe, for a period of 56 years. Components exhibiting slow temporal behavior were extracted using DSS with linear denoising. The first component, most prominent in the interannual time scale, captured the well-known El Niño-Southern Oscillation (ENSO) phenomenon and the second component was close to the derivative of the first one. The slow components extracted in a wider frequency range were further rotated using a frequency-based separation criterion implemented by DSS with nonlinear denoising. The rotated sources give a meaningful representation of the slow climate variability as a combination of trends, interannual oscillations, the annual cycle and slowly changing seasonal variations. Again, components related to the ENSO phenomenon emerge very clearly among the found sources.
authors.affiliation: Laboratory of Computer and Information Science, Helsinki University of Technology, P.O. Box 5400, FI-02015 TKK, Espoo, Finland. alexander.ilin@tkk.fi
authors.forename: Alexander
authors.initials: A
authors.lastname: Ilin
authors.forename: Harri
authors.initials: H
authors.lastname: Valpola
authors.forename: Erkki
authors.initials: E
authors.lastname: Oja
mesh_terms: D001274:Atmospheric Pressure; D002980:Climate; D019015:Geologic Sediments; D015233:Models, Statistical; D009792:Oceans and Seas; D012621:Seasons; D013057:Spectrum Analysis; D013696:Temperature; D013997:Time Factors