Effects of different reference periods on drought index (SPEI) estimations from 1901 to 2014
This study aims to understand how different reference periods (i.e., calibration periods) of climate data used to estimate drought indices influence regional drought assessments. Specifically, we investigate the influences of different reference periods on historical drought characteristics, suc...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-10-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/21/4989/2017/hess-21-4989-2017.pdf |
| Summary: | This study aims to understand how different reference periods
(i.e., calibration periods) of climate data used to estimate drought indices
influence regional drought assessments. Specifically, we investigate the
influences of different reference periods on historical drought
characteristics, such as the trend, frequency, intensity and spatial extent,
using the standardized precipitation evapotranspiration index (SPEI) with a
12-month lag (SPEI-12), which was 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 to compute the SPEI: P1 and P2 together, P1 and P2
separately and P1 only. Focusing on East Asia, Europe, the United States and
West Africa, we find that the influence of the reference period is
significant in East Asia and West Africa, with dominant drying trends from P1
to P2. The reference period influenced the assessment of drought
characteristics, particularly the severity and spatial extent, whereas the
influence on the frequency was relatively small. Finally, self-calibration,
which is the most common practice for indices such as the 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 by the use of two global datasets, they highlight the need for
clarification of the reference period in drought assessments to better
understand regional drought characteristics and the associated temporal
changes, particularly under climate change scenarios. |
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| ISSN: | 1027-5606 1607-7938 |