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| Titel |
Trends and extremes of drought indices throughout the 20th century in the Mediterranean |
| VerfasserIn |
P. M. Sousa, R. M. Trigo, P. Aizpurua, R. Nieto, L. Gimeno, R. Garcia-Herrera |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 11, no. 1 ; Nr. 11, no. 1 (2011-01-05), S.33-51 |
| Datensatznummer |
250009035
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| Publikation (Nr.) |
 copernicus.org/nhess-11-33-2011.pdf |
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| Zusammenfassung |
Average monthly precipitation, the original Palmer Drought Severity Index
(PDSI) and a recent adaptation to Europe, the Self Calibrated PDSI (scPDSI)
have been used here to analyse the spatial and temporal evolution of drought
conditions in the Mediterranean during the 20th century. Monthly, seasonal
and annual trends were computed for the period 1901–2000 and also for the
first and second halves of this period. The statistical significance of
trends was obtained with a modified version of the Mann-Kendall test that
accounts for serial auto-correlation. The results show a clear trend towards
drier conditions during the 20th century in most western and central
Mediterranean regions, with the exceptions of northwestern Iberia and most of
Turkey that reveal an increase of moisture availability. A Generalized
Extreme Values (GEV) analysis was applied to the maximum and minimum regional
values of scPDSI, with results pointing towards a significant decline of
absolute extreme values in central areas (Italy and Balkans) and a less clear
picture emerging in western (Iberia) and eastern (Turkey) realms.
The inter-annual variability of the scPDSI index series is shown to be more
realistic than the corresponding PDSI version, fitting better the drought
episodes sequence and magnitude described in the literature for each
sub-region. We assess the decadal and inter-annual variability of the scPDSI
for each sub-domain and evaluate the role played by the major teleconnection
patterns, and by several sea surface temperature (SST) anomalies. The main
driver of scPDSI in western and central Mediterranean areas is the winter
North Atlantic Oscillation (NAO) pattern that is also relevant during the
following spring and summer seasons with anti-correlation values below
−0.60. The second most important mode corresponds to the Scandinavian
Pattern that is significantly associated to the scPDSI between winter and
summer over central Mediterranean (correlation values around 0.50). Finally,
the teleconnection and SST analysis has allowed us to calibrate a stepwise
regression model, enabling the forecasting of summer drought conditions six
months in advance. The final model obtained is capable of reproducing the
observed scPDSI time series fairly well, with a correlation coefficient of
0.79 (0.77 after cross-validation) and a significant gain over climatology
(SSc=59%), while the corresponding result against persistence is
more modest (SSp6=11%). |
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