Long term precipitation trends and variability within the Mediterranean region
Other literature type
Philandras, C. M.
Nastos, P. T.
Douvis, K. C.
Zerefos, C. S.
(issn: 1684-9981, eissn: 1684-9981)
In this study, the trends and variability of annual precipitation totals and
annual rain days over land within the Mediterranean region are analyzed.
Long term ground-based observations concerning, on one hand, monthly
precipitation totals (1900–2010) and rain days (1965–2010) from 40
meteorological stations within the Mediterranean region were obtained from
the Hellenic National Meteorological Service and the World Climate Data and
Monitoring Programme (WCDMP) of the World Meteorological Organization. On
the other hand, high spatial resolution (0.5° × 0.5°) gridded
monthly data CRU TS 3.1 were acquired from the Climatic Research
Unit, University of East Anglia, for the period 1901–2009. The two datasets
were compared by means of trends and variability, while the influence of the
North Atlantic Oscillation (NAO) in the Mediterranean precipitation was
examined. In the process, the climatic changes in the precipitation regime
between the period 1961–1990 (reference period) and the period 2071–2100
(future climate) were presented using climate model simulations
(RACMO2.1/KNMI). The future climate
projections were based on SRES A1B.
The findings of the analysis showed that statistically significant (95%
confidence level) negative trends of the annual precipitation totals exist
in the majority of Mediterranean regions during the period 1901–2009, with
an exception of northern Africa, southern Italy and western Iberian
peninsula, where slight positive trends (not statistically significant at
95% CL) appear. Concerning the annual number of rain days, a pronounced
decrease of 20 %, statistically significant (95% confidence level),
appears in representative meteorological stations of east Mediterranean,
while the trends are insignificant for west and central Mediterranean. Additionally,
NAO index was found to be anticorrelated with the precipitation
totals and the number of rain days mainly in Spain, southern France, Italy
and Greece. These correlations are higher within the rain season
(October–March) than the entire year. Based on the results of regional
climate model RACMO2.1/KNMI, precipitation is very likely to decrease almost
20% in the period 2071–2100 compared to 1961–1990, under SRES A1B.