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Archetypal Analysis: Mining Weather and Climate Extremes
Stockholm University, Faculty of Science, Department of Meteorology .
Number of Authors: 2
2017 (English)In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 30, no 17, 6927-6944 p.Article in journal (Refereed) Published
Abstract [en]

Conventional analysis methods in weather and climate science (e.g., EOF analysis) exhibit a number of drawbacks including scaling and mixing. These methods focus mostly on the bulk of the probability distribution of the system in state space and overlook its tail. This paper explores a different method, the archetypal analysis (AA), which focuses precisely on the extremes. AA seeks to approximate the convex hull of the data in state space by finding corners'' that represent pure'' types or archetypes through computing mixture weight matrices. The method is quite new in climate science, although it has been around for about two decades in pattern recognition. It encompasses, in particular, the virtues of EOFs and clustering. The method is presented along with a new manifold-based optimization algorithm that optimizes for the weights simultaneously, unlike the conventional multistep algorithm based on the alternating constrained least squares. The paper discusses the numerical solution and then applies it to the monthly sea surface temperature (SST) from HadISST and to the Asian summer monsoon (ASM) using sea level pressure (SLP) from ERA-40 over the Asian monsoon region. The application to SST reveals, in particular, three archetypes, namely, El Nino, La Nina, and a third pattern representing the western boundary currents. The latter archetype shows a particular trend in the last few decades. The application to the ASM SLP anomalies yields archetypes that are consistent with the ASM regimes found in the literature. Merits and weaknesses of the method along with possible future development are also discussed.

Place, publisher, year, edition, pages
2017. Vol. 30, no 17, 6927-6944 p.
Keyword [en]
Pattern detection
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:su:diva-147042DOI: 10.1175/JCLI-D-16-0798.1ISI: 000407276600018OAI: oai:DiVA.org:su-147042DiVA: diva2:1143075
Available from: 2017-09-20 Created: 2017-09-20 Last updated: 2017-09-20Bibliographically approved

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