Precipitation Scenarios in the Central-western
Mediterranean Basin
E. Piervitali, M. Colacino
Abstract
The increase of greenhouse gases in the atmosphere could modify the
hydrological cycle, in particular the rainfall regime. With reference to the
Mediterranean basin, an analysis of precipitation in the period 1951-1995,
indicates a rainfall reduction of 20%. On the basis of this trend a forecast of
precipitation till 2030 has been performed using Winter's statistical model,
which has been applied considering the Mediterranean Oscillation as forcing
factor of climate. The obtained predictions show a rainfall decrease,
particularly strong in the southern regions. In addition the soil moisture has
been evaluated, using De Martonne's index. The results indicate a risk of
desertification in some regions, due to the drying up of the soil in the future.
1 Introduction
Several investigations have been devoted to global change, in particular to study the
variation in precipitation pattern, related to the important problem of the water
resources availability.
Scenario models, based on the use of GCM, pay particular attention to this
matter. They indicate an increase ofthe temperature between I cC and 3SC in 2100
and the global mean precipitation should increase about 3% to 15% (IPCC-WG 1,
1995), however they do not give uniform variation on the globe about the trend of
precipitations, because an increase is foreseen for high latitudes, while a reduction
is expected in the low ones (Palutikof and Wigley, 1996).
In addition, the forecast at the regional scale presents great uncertainties, because
the results obtained by using General Circulation Models (GCM) are largely
different or contradictory, particularly in the assessment of precipitation trend. One
problem is the relatively coarse spatial resolution of GCMs with respect to the fine
resolution required by regional scenarios (Henderson-Sellers and Hansen, 1995).
Due to this large differences it is suitable to face the following two problems:
Mediterranean Basin
E. Piervitali, M. Colacino
Abstract
The increase of greenhouse gases in the atmosphere could modify the
hydrological cycle, in particular the rainfall regime. With reference to the
Mediterranean basin, an analysis of precipitation in the period 1951-1995,
indicates a rainfall reduction of 20%. On the basis of this trend a forecast of
precipitation till 2030 has been performed using Winter's statistical model,
which has been applied considering the Mediterranean Oscillation as forcing
factor of climate. The obtained predictions show a rainfall decrease,
particularly strong in the southern regions. In addition the soil moisture has
been evaluated, using De Martonne's index. The results indicate a risk of
desertification in some regions, due to the drying up of the soil in the future.
1 Introduction
Several investigations have been devoted to global change, in particular to study the
variation in precipitation pattern, related to the important problem of the water
resources availability.
Scenario models, based on the use of GCM, pay particular attention to this
matter. They indicate an increase ofthe temperature between I cC and 3SC in 2100
and the global mean precipitation should increase about 3% to 15% (IPCC-WG 1,
1995), however they do not give uniform variation on the globe about the trend of
precipitations, because an increase is foreseen for high latitudes, while a reduction
is expected in the low ones (Palutikof and Wigley, 1996).
In addition, the forecast at the regional scale presents great uncertainties, because
the results obtained by using General Circulation Models (GCM) are largely
different or contradictory, particularly in the assessment of precipitation trend. One
problem is the relatively coarse spatial resolution of GCMs with respect to the fine
resolution required by regional scenarios (Henderson-Sellers and Hansen, 1995).
Due to this large differences it is suitable to face the following two problems: