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Authors
Advisor(s)
Abstract(s)
Distinction between drought and aridity is crucial
to understand water scarcity processes. Drought indices
are used for drought identification and drought severity
characterisation. The Standardised Precipitation Index
(SPI) and the Palmer Drought Severity Index (PDSI) are the
most known drought indices. In this study, they are compared
with the modified PDSI for Mediterranean conditions
(MedPDSI) and the Standardised Precipitation Evapotranspiration
Index (SPEI). MedPDSI results from the soil water
balance of an olive crop, thus real evapotranspiration is
considered, while SPEI uses potential (climatic) evapotranspiration.
Similarly to the SPI, SPEI can be computed at
various time scales. Aiming at understanding possible impacts
of climate change, prior to compare the drought indices,
a trend analysis relative to precipitation and temperature
in 27 weather stations of Portugal was performed for the
period 1941 to 2006. A trend for temperature increase was
observed for some weather stations and trends for decreasing
precipitation in March and increasing in October were also
observed for some locations. Comparisons of the SPI and
SPEI at 9- and 12-month time scales, the PDSI and Med-
PDSI were performed for the same stations and period. SPI
and SPEI produce similar results for the same time scales
concerning drought occurrence and severity. PDSI and Med-
PDSI correlate well between them and the same happened
for SPI and SPEI. PDSI and MedPDSI identify more severe
droughts than SPI or SPEI and identify drought occurrence
earlier than these indices. This behaviour is likely to be related
with the fact that a water balance is performed with
PDSI and MedPDSI, which better approaches the supplydemand
balance.
Description
Keywords
climate drought indices precipitation evapotranspiration
Pedagogical Context
Citation
"Natural Hazards and Earth System Sciences". ISSN 1561-8633. 12 (2012) 1481-1491