A synthesis of the time-scale variability of commonly used climate indices using continuous wavelet transform

• Published in: Global and Planetary Change
• Main Authors: Rossi, A., Massei, Nicolas, Laignel, Benoît
• Other Authors: Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: climate indices; climate variability; climate fluctuations; climate shifts; continuous wavelet transform; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; environment; [SDE.MCG]Environmental Sciences/Global Changes; Pacific; Soi; North Atlantic; North Atlantic oscillation
• Online Access: https://hal.archives-ouvertes.fr/hal-00735683; https://doi.org/10.1016/j.gloplacha.2011.04.008

International audience Climate indices are commonly used as indicators of climate variations and very often compared to those of environmental processes (geophysical, hydrological, ecological, etc.) in order to understand them in terms of regional- to global-scale fluctuations. Through their use in many research fields and published works, it appears that (sometimes not so) slight differences may exist in the identification of the characteristic time-scales governing the temporal variations of those indices from one work to another, and one eventually may experience difficulties in finding a "unified" referencing of these typical scales of variability. For this purpose, we propose a synthetic description and quantification of the time-scale variability of some of the most commonly used climate indices: the Atlantic Multidecadal Oscillation (AMO), the North Atlantic Oscillation (NAO), the Northern Annular Mode (NAM), the Pacific Decadal Oscillation (PDO), the Southern Oscillation Index (SOI) and the Pacific-North-America teleconnection (PNA); which was performed using a single unified methodology, i.e. continuous wavelet analysis, adapted to the study of stochastic processes that exhibit time-varying statistical characteristics. Each climate index presents its own characteristic time-scales, from inter-annual to multi-decadal scales. However, some energy bands present common characteristics in terms of frequency (or time-scale) ranges and/or temporal occurrence, from inter-annual scale (a group of 2-4 y, 3-6 y and 4-8 y fluctuations), to (pluri-)decadal scale (a group of 5-12 y, 8-16 y, 12-20 y and 17-30 y fluctuations) and in the long term (a group of 20-50 y, 40-60 y and 50-80 y fluctuations). Moreover, a common structuration for all climate indices seems to appear in the form of an inter-annual scale structuration in 1930, and a global shift in the frequency structuration of all climate indices in 1970 affecting decadal and pluri-decadal scales. Analysis of the distribution of the total variance of climate ...