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Earth System Dynamics An interactive open-access journal of the European Geosciences Union

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https://doi.org/10.5194/esd-2016-47
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
25 Oct 2016
Review status
This discussion paper is a preprint. It has been under review for the journal Earth System Dynamics (ESD). The manuscript was not accepted for further review after discussion.
Identifying global patterns of stochasticity and nonlinearity in the Earth System
Fernando Arizmendi1, Marcelo Barreiro1, and Cristina Masoller2 1Instituto de Física, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo, Uruguay
2Departament de Física, Universitat Politecnica de Catalunya, 08222 Terrassa, Barcelona, Spain
Abstract. We demonstrate that two simple measures of time series analysis are able to capture different dynamical and statistical properties of large-scale atmospheric phenomena. We consider two surface air temperature (SAT) datasets, covering a spatial grid of points over the Earth surface (NCEP CDAS1 and ERA Interim reanalysis). In each location we analyze i) the distance between the lagged SAT time series and the insolation (i.e., the local top-of-atmosphere incoming solar radiation), and ii) the Shannon entropy computed from the probability distribution function (pdf) of SAT values. The distance quantifies the similarity between the lagged SAT waveform and the isolation waveform, while the entropy, as defined in information theory, measures the degree of disorder or uncertainty of each time series, which we refer to as stochasticity: the entropy captures the shape of the SAT pdf and is maximum when the pdf is uniform. With the distance measure we uncover well-defined spatial patterns formed by regions with similar SAT response to solar forcing, while with the entropy measure, we uncover regions that have SAT pdf of similar shape. The entropy analysis also allows identifying the geographical regions in which SAT time series has extreme values (i.e., values which are extreme in the local statistics), because the long-tail shape of the pdf is captured as low entropy values. We uncover significant differences between the NCEP CDAS1 and ERA Interim datasets in specific geographical regions, which are due to the presence of extreme values in one dataset but not in the other. In this way, the entropy maps are a valuable tool for anomaly detection and model inter-comparisons.

Citation: Arizmendi, F., Barreiro, M., and Masoller, C.: Identifying global patterns of stochasticity and nonlinearity in the Earth System, Earth Syst. Dynam. Discuss., https://doi.org/10.5194/esd-2016-47, 2016.
Fernando Arizmendi et al.
Fernando Arizmendi et al.

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Short summary
We analyze the dynamical and statistical properties of two surface air temperature (SAT) reanalysis datasets. For each SAT time-series we analyze i) the distance between the lagged SAT time series and the insolation, and ii) the Shannon entropy computed from the probability distribution function (pdf) of SAT values. We show that these simple measures uncover meaningful long-range coherent spatial structures that emerge from the local properties of SAT time-series.
We analyze the dynamical and statistical properties of two surface air temperature (SAT)...
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