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Water 2015, 7(12), 7045-7065; doi:10.3390/w7126673

Linear Trend Detection in Serially Dependent Hydrometeorological Data Based on a Variance Correction Spearman Rho Method

1,* , 1,†
,
2,†
and
1,†
1
College of Hydrology and Water Resources, Hohai University, Nanjing 210098, China
2
Department of Earth, Environmental and Geospatial Sciences, Lehman College, City University of New York, Bronx, New York, NY 10468, USA
These authors contributed equally to this work.
*
Author to whom correspondence should be addressed.
Academic Editor: Athanasios Loukas
Received: 20 July 2015 / Revised: 20 November 2015 / Accepted: 10 December 2015 / Published: 17 December 2015
View Full-Text   |   Download PDF [9196 KB, uploaded 23 December 2015]   |  

Abstract

Hydrometeorological data are commonly serially dependent and thereby deviate from the assumption of independence that underlies the Spearman rho trend test. The presence of autocorrelation will influence the significance of observed trends. Specifically, the positive autocorrelation inflates Type І errors, while it deflates the power of trend detection in some cases. To address this issue, we derive a theoretical formula and recommend an appropriate empirical formula to calculate the rho variance of dependent series. The proposed procedure of the variance correction for the Spearman rho method is capable of mitigating the effect of autocorrelation on both, Type І error and power of the test. Similar to the Block Bootstrap method, it has the advantage that it does not require an initial knowledge of the autocorrelation structure or modification of the series. In comparison, the capability of the Pre-Whitening method is sensitive to model misspecification if the series are whitened by a parametric autocorrelation model. The Trend-Free Pre-Whitening method tends to lead to an overestimation of the statistical significance of trends, similar to the original Spearman rho test. The results of the study emphasize the importance of selecting a reliable method for trend detection in serially dependent data. View Full-Text
Keywords: Spearman rho; trend test; autocorrelation; hydrometeorological time series Spearman rho; trend test; autocorrelation; hydrometeorological time series
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Wang, W.; Chen, Y.; Becker, S.; Liu, B. Linear Trend Detection in Serially Dependent Hydrometeorological Data Based on a Variance Correction Spearman Rho Method. Water 2015, 7, 7045-7065.

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