Detecting Changes in Forced Climate Attractors with Wasserstein Distance

• DOI: 10.5194/npg-2017-5
• Publication Date: 2017-02-20T07:18:01Z
• Authors: Yoann Robin; Pascal Yiou; Philippe Naveau
• Keywords: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere; QC801-809; Science; Physics; QC1-999; Q; Geophysics. Cosmic physics; 0207 environmental engineering; 02 engineering and technology; [SDU.ENVI] Sciences of the Universe [physics]/Continental interfaces, environment; 13. Climate action; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces; [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment; environment

Abstract. The climate system can been described by a dynamical system and its associated attractor. The dynamics of this attractor depends on the external forcings that influence the climate. Such forcings can affect the mean values or variances, but regions of the attractor that are seldom visited can also be affected. It is an important challenge to measure how the climate attractor responds to different forcings. Currently, the Euclidean distance or similar measures like the Mahalanobis distance have been favoured to measure discrepancies between two climatic situations. Those distances do not have a natural building mechanism to take into account the attractor dynamics. In this paper, we argue that a Wasserstein distance, stemming from optimal transport theory, offers an efficient and practical way to discriminate between dynamical systems. After treating a toy example, we explore how the Wasserstein distance can be applied and interpreted to detect non-autonomous dynamics from a Lorenz system driven by seasonal cycles and a warming trend.