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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2016-445
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
19 Sep 2016
Review status
This discussion paper is under review for the journal Hydrology and Earth System Sciences (HESS).
Effects of different reference periods on drought index estimations for 1901–2014
Myoung-Jin Um1, Yeonjoo Kim1, Daeryong Park2, and Jeong Bin Kim1 1Department of Civil and Environmental Engineering, Yonsei University, Seoul, 03722, Republic of Korea
2Department of Civil, Environmental and Plant Engineering, Konkuk University, Seoul 05029, Republic of Korea
Abstract. This study aims to understand how different reference periods (i.e., calibration periods) of climate data for estimating the drought index influence regional drought assessments. Specifically, we investigate the influence of different reference periods on historical drought characteristics such as trends, frequency, intensity and spatial extents using the standard precipitation evapotranspiration index with a 12-month lag (SPEI-12) estimated from the datasets of the climate research unit (CRU) and the University of Delaware (UDEL). For the 1901–1957 (P1) and 1958–2014 (P2) estimation periods, three different types of reference periods are used: P1 and P2 together, P1 and P2 separately and P1 only. Focusing on East Asia, Europe, North America and West Africa, we find the influence of the reference periods to be significant in East Asia and West Africa, with dominant drying trends from P1 to P2. The reference periods influence the assessment of drought characteristics, particularly for severity and spatial extent, whereas their influence on the frequency is relatively small. Finally, self-calibration, which is the most common practice with an index such as SPEI, tends to underestimate the drought severity and spatial extent relative to the other approaches used in this study. Although the conclusions drawn in this study are limited to two global datasets, they nevertheless highlight the need for the reference period to be clarified in drought assessments to better understand regional drought characteristics and their temporal changes, particularly under climate change scenarios.

Citation: Um, M.-J., Kim, Y., Park, D., and Kim, J. B.: Effects of different reference periods on drought index estimations for 1901–2014, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2016-445, in review, 2016.
Myoung-Jin Um et al.
Myoung-Jin Um et al.
Myoung-Jin Um et al.

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This study aims to understand how different reference periods (i.e., calibration periods) of climate data for estimating the drought index influence regional drought assessments. Specifically, we investigate the influence of different reference periods on historical drought characteristics such as trends, frequency, intensity and spatial extents using the standard precipitation evapotranspiration index (SPEI) estimated from the two widely used global datasets.
This study aims to understand how different reference periods (i.e., calibration periods) of...
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