Analyzing and comparing complex environmental time series using a cumulative sums approach

Peter Regier; Henry Briceño; Joseph N Boyer

doi:10.1016/j.mex.2019.03.014

Analyzing and comparing complex environmental time series using a cumulative sums approach

MethodsX. 2019 Apr 9:6:779-787. doi: 10.1016/j.mex.2019.03.014. eCollection 2019.

Authors

Peter Regier¹, Henry Briceño², Joseph N Boyer³

Affiliations

¹ Center for Water and the Environment, University of New Mexico, Albuquerque, NM, United States.
² Southeast Environmental Research Center, Florida International University, Miami, FL, United States.
³ Center for Research & Innovation, Plymouth State University, Plymouth, NH, United States.

Abstract

Cumulative sums (Cusums) are a simple, efficient statistical method developed for process control and increasingly used to determine underlying features of time series. Here, two useful applications of Cusums to environmental time series are presented: Cusums in the time domain and plotting Cusum-transformed variables against non-transformed variables to extract meaning in the context of driver-response relationships. These statistical analyses are simple to conduct and provide valuable information about trends, patterns and thresholds of time-series over time and in relation to potential driver variables. In addition, this work investigates the robustness of the Cusum transform to various characteristics of environmental time series that challenge conventional statistical methods. In summary, this work presents: •Cusum methods to derive meaning from complex environmental time series.•Effects of common time series issues on the Cusums method.•Application to real-world datasets.

Keywords: Applying cumulative sums to environmental data; Cumulative sums; Driver-response; Everglades restoration; Nutrients; Time series; Water management.