254
p= [~+ r· PI l IWr- L
p=[~+r.pJI
(r+L\
t+r-integerl _)IL
. L
E. Piervitali, M. Colacino
ifr~ L
ifr? L
(4)
and a, b, c are three smoothing constants between 0 and 1, calculated by the
minimization of the square difference between the theoretic series, defined by the
above equations, and the observed series.
The obtained prediction, for the 500 hPa surface, is shown in Fig.5. Values until
1995 are observed data, while values from 1996 to 2030 are the predictions. In Fig.5
also the linear trend is shown, that is a positive trend, and the simple 7 term
weighted average, that indicate an oscillation of about 22 years.
The prediction of the mean precipitation over the Central Western
Mediterranean
has been obtained using the anticorrelation between the Mediterranean Oscillation
E
£?
.!:
o
o
LO
5860 - , - - - - - - - - - - - - - - - - - - - - - - - ,
5840
5820
5800
5780
5760
5740
5720
5700
5680 4-------.-------.------.------~------~
1940
1960
1980
2000
2020
2040
year
Fig.S. 500 hPa pressure pattern in Algiers station with the relative linear trend and the
simple 7 -term weighted moving average: observations until 1995 and forecast from
1996 until 2030, using Winter's model